Flybywire, you did the right thing. The Captain may not land until the cabin is ready, and needs to know when it is ready.
The pax may have had a rather urgent need for the loo, maybe he was just being a total idiot, but you did what you are required to do...you advised the Captain that the cabin was no longer ready. It now becomes her decision whether the go-around or not. Her options are delineated by a number of factors (weather, fuel remaining, etc), and she would have to make a decision based on those factors, and the trouble she would inevitably find herself in if she had landed with someone still on the potty. That there was still time enough before landing for the pax to do his business, and the cabin to be restored to the ready state, shows the Captains trust in you to fix the problem before landing, before she took the drastic action of having to go-around for repositioning.
So you did a good job. Don't stress too much over it. Remember, the pax had probably packed his brain in with his checked-in baggage
