It is enough to check for your deposits only. If you follow your deposit tx (assuming it exists in the first place) and see that those funds were never spent from that multisig address that starts with 3, that means they are still locked. Otherwise, they are either in your wallet, but Bisq isn’t showing them or they have somehow been awarded to the other trader for some reason, which I doubt is the case.
Most likely there was some issue with the deposit tx getting broadcasted and funds never left your wallet, in that case this can be solved easily on your end.
No, there is no back-end for Bisq like that. Bisq is fully P2P, users and users only are in control of the funds and there is no one else that can access them for you. Bisq is really fully decentralized and does it’s best to preserve user’s privacy as well, so there is very little that anybody can do without trader’s help.