one day I experienced a heavy delay (more than 10 hours) to receive the payment. I was not worried because already the customer had shown me his device to check the network confirmation (from his end, it was showing about 15 network confirmation), but I never received payment.
Although you were not worried, you sounded a bit worried based on your reaction and checking from the customer's side for confirmation.
Even without checking the customer's transaction history, you can do it from your own end by using any Bitcoin explorer, which can show off both unconfirmed transactions, provided it's not an internal transfer.
If the transaction is successful, why Binance is undergoing its second confirmation, you will still be notified via email of a successful deposit even though you will not be allowed to exchange or withdraw the bitcoin until it's fully confirmed.
I have experienced a similar network delay, but it was from blockchain confirmation that day, not anything relating to exchange.