Have I "lost" my Bitcoins?

[Amandrax]

On 2nd December, I attempted a to make my first purchase with bitcoins from my electrum wallet. What I was did not know, was that the transaction HAD to be completed within one hour. Being a newbie, I set the transaction rate as low as possible (£0.02). And of course, the transaction was not completed within the hour. Thus, the vendor cancelled the transaction.
However, my electrum wallet shows the amount as having been paid, and has been deducted from my wallet. SO, where did my bitcoins go to (are they lost in cyberspace?) or will they be returned to my wallet in due course? In addition, the refund address that I generated has expired (Seven days is the maximum time that electrum allows an address to exist).

[ranochigo]

SO, where did my bitcoins go to (are they lost in cyberspace?) or will they be returned to my wallet in due course?

No. Is the transaction confirmed? If it's still unconfirmed, there's a chance that it could be dropped by the mempool and it'll be appear as if the transaction has never happened. If the transaction is confirmed, the funds are in the recipient address.

In addition, the refund address that I generated has expired (Seven days is the maximum time that electrum allows an address to exist).

Common misconception. The expiry for the address generated in the receive tab is merely an invoice and you can set it to expire at any time for easier accounting. However, addresses themselves never expire and will always be in the wallet that has the correct seed.

[HCP]

SO, where did my bitcoins go to (are they lost in cyberspace?) or will they be returned to my wallet in due course?

If the transaction is "confirmed", then the vendor (or their payment gateway provider) has your coins. You'll most likely need to contact them directly to request a refund.

Do you know what the payment gateway was? Was it BitPay?
 

In addition, the refund address that I generated has expired (Seven days is the maximum time that electrum allows an address to exist).

No, it hasn't... the addresses in Electrum do not "expire"... the "invoice" that you created on the "Receive" tab might display as "expired", but it's just a book-keeping thing in Electrum... the address will be valid forever (assuming you don't lose access to the wallet )

[The Cryptovator]

Bitcoin is irreversible, so if the transaction is confirmed on the blockchain then it's never possible to refund on your wallet. If the transaction is not yet confirmed then it's possible to move the fund by double-spending. Otherwise, there is only one way to recover your funds by contacting the vendor. The Bitcoin address has been generating from the vendor's Marchant wallet. Means funds should exist in their wallet at the end. Bitcoin wouldn't lose in cyberspace unless you burn it or sent it to on wrong/random addresses. So, only the seller/vendor could help you if they are honest with their business.

[NotATether]

Since you paid the lowest in fees which was £0.02 or 140 satoshis at the time, I'm guessing you paid 1 satoshi/byte and your transaction is stuck in the mempool. But it's impossible to confirm this if you don't share the transaction ID with us.

See the thread All about "stuck" transactions and what you can do to fix them and look at the sections "waiting for the network to forget about a transaction" and the sections about RBF.

You might also be able to double-spend the bitcoins back to your address if you turned on RBF for that transaction (it is on by default).

[AB de Royse777]

And of course, the transaction was not completed within the hour. Thus, the vendor cancelled the transaction.

Whoever the vendor is - it's very bad practice. Possibly they do not have much idea about Bitcoin network. Around at 4 to 5 am GMT your tx got confirmed which means they have your money now. You just need to contact them and get a refund. Give them an address from the same wallet so that they can refund you.

You might also be able to double-spend the bitcoins back to your address if you turned on RBF for that transaction (it is on by default).

He could but I bet he does not know how to do that. Besides the tx fees were not much. When I checked it was around 2 sat for the next block.

[Amandrax]

The transaction has NOT been confirmed, so the coins are not with the vendor.
NotATether was absolutely spot on-- I did indeed pay 1 satoshi/byte, so the 'stuck in the mempool' theory seems highly plausible.
I am happy to share the transaction ID, which is 3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155.

[LoyceV]

I am happy to share the transaction ID, which is 3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155.

This transaction was confirmed 8 days ago.
That means:

the vendor (or their payment gateway provider) has your coins. You'll most likely need to contact them directly to request a refund.

[HCP]

The transaction has NOT been confirmed, so the coins are not with the vendor.
NotATether was absolutely spot on-- I did indeed pay 1 satoshi/byte, so the 'stuck in the mempool' theory seems highly plausible.
I am happy to share the transaction ID, which is 3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155.

Unfortunately, that transaction has been confirmed...


https://btc.com/3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155
https://blockchair.com/bitcoin/transaction/3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155
https://live.blockcypher.com/btc/tx/3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155/
https://www.blockchain.com/btc/tx/3b15b25d0b3effadf66546e6f52934f4b03bd38c52b5c69137467d2b6c912155

Additionally, the 0.00135181 BTC (which I am guessing you sent, based on the address types of the outputs), has already been "spent" (moved) by whomever you sent the coins to (in this transaction

Contact the vendor and/or their payment gateway provider, it's the only way you're going to get your coins (or your order).

[NotATether]

Contact the vendor and/or their payment gateway provider, it's the only way you're going to get your coins (or your order).

Payment gateways cannot assist people in getting refunds once the transaction is confirmed, because the money is not in the hands of the payment gateway anymore. If they send any invoices to emails they usually write that too. Only the vendor can return the funds at that point.

[HCP]

Depends on the payment gateway... and how you choose to handle settlement... BitPay offers a facility where they pay vendors in fiat, crypto or a combination of the two...

Regardless, no one here can help the OP, they will need to contact either the Vendor and/or the payment gateway provider to figure out how to start a refund process (or get their order processed)