Bought XMR and did not check monero wallet to confirm the XMR was actually sent but I confirmed the transaction.Upon checking my monero wallet, i saw that nothing was actually sent and the transaction ID does not show up in xmrchain. Is it too late to open a dispute and have my BTC returned?"
If you are the seller, and you released the btc to the buyer, the funds have been transferred so there is no way to reclaim them anymore, I’m afraid. Only hope is that buyer comes around and completes his side of the trade, but you can also contact support staff on matrix, at bisq.chat sending evidence of this, and in case we get mediations with him in the future we could intercept him