When block explorers don’t show a transaction we can probably safely assume that the problem was in Bisq and that the transaction was never published, so it almost certainly isn’t because of the congestion on the Bitcoin network.
You never risk losing funds in Bisq as long as you have your seed words. Only when you have open trades (not offers, but actual ongoing trades) your funds are not in your wallet so in those cases you need to contact the arbitrator (over the forum for example). So deleting the SPV chain file should be a safe operation. You can also try using an emergency wallet tool with alt+e and withdraw your funds.
Either way, nothing to worry about. Your seed words can actually always be imported into a wallet such as Electrum and you can access your bitcoins that way. BTC don’t really get lost in Bisq.