I sold some BTC & received payment in my bank account, yet there was no request to send BTC. The transaction is marked as completed, what was the source of the BTC?
If you are the maker when you create the offer to sell bitcoin it allocates funds in your bitcoin wallet for the security deposit and trade amount. When the trade is taken the funds get locked in a multsig and once you confirm payment was received the trade pays out.
If you were the taker you locked your deposit and trade amount at the time the offer is taken. Once you confirm payment the funds are released.
Have a look at the Bisq wiki Bisq 1 - Bisq Wiki this is a good place for information about how everythign works.