To be honest, I have no idea either.
Because the mobile and desktop versions both show the same behavior.

All I can suggest is to create a copy of your wallet by using "I already have a seed" and see if it will generate the same wallet and set of addresses.

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-update-

Okay, you need to differentiate inputs from outputs, example (from testnet):


Your transaction shows that it has 14 inputs and 1 output.
So, what you mean is it has 13 yellow-highlighted inputs and 1 green-highlighted input.
The output is not highlighted.

We're now back to the possibility that your seed phrase was hacked.

It will be highlighted as "red" if it's out of your gap limit and "not highlighted" if it's not currently in the keypool.
There's definitely something weird going on here.

What's you're Electrum's version?

Go to console tab and use the code below to generate more addresses.


The number 50 in the code above is number of addresses generated by Electrum. You can change it to any other number.

What do you mean by all the outputs? The transaction you posted has only 1 output. I think you meant inputs. right?

If that's the case, it means that all 14 inputs of the transaction had been used as change addresses before.
Also, the address highlighted in green is yours. If that's the receiving address, you should have access to the fund.

According to wallet explorer, all 14 inputs belong to the same wallet (I'm not sure how the site determines that though). Seeing the ammounts of satoshis in the tx, it doesn't really look like a hacker may have been bothered; some of the inputs are as small as 500 satoshis; and to me, this just looks like a transaction to consolidate all your small inputs. And all of the inputs are change addresses, used only once...

You saying that most of the addresses used there kind of reinforces that theory, so... Did you try installing the wallet in Electrum as it was suggested earlier? The app shouldn't create transactions by itself, but for what you've told, I'm pretty confident it was a consolidation tx. If you install Electrum on your computer, and check it's connected; check if the funds do show, and if they don't, try increasing the gap limit.

If none of that works, I'm pretty clueless. Bitcoin core does have a command to check whether an address belongs to the wallet in use; but I'm unaware of Electrum having a similar feature

I think what you said is impossible having a transaction that you didn't know and make your balance zero. Maybe you just neglect that you made that transaction or there is someone that also know your private key and did that without your knowing. Always be careful with your private key to make your funds secured.

This is not an issue with change addresses then. Your wallet will not make transaction on its own, regardless of what selection you made regarding using or not using change addresses. If you absolutely did not make that transaction, then your wallet has been compromised and someone else has made that transaction to steal your coins.

Did anyone else have access to your phone? Where did you download the Android app from? How did you back up your seed phrase?