My airline's policy is not to lock the toliet doors. We just have to check that nobody is in the toilet for take off and landing as part of our cabin secure checks. I have seen in other airlines people who lock them open to make sure nobody goes in but I don't do it as I think it's not a good fire prevention procedure.
When this pax went to the loo the gear was already down and we were strapped in. It was also very windy and quite rough!! If we hadn't done anything he probably would have ended up landing inside the toilet. I didn't feel like ignoring the thing!
If he had hurt himself (however badly) my colleague and I (neither the captain nor the f/o) would have been the ones stuck there trying to help him, etc. Lots of hassle not to say that a more serious medical situation (Imagine he had seriously hit his head on landing) is the last thing a cabin crew wants!!!!!!!!!!!!!!
I also know though that a go around not always is the safest option and I don't want to be standing in the cabin if a go around is initiated. I do not want to put my safety at risk because somebody can't be bothered to comply to safety regulations!!
Tricky.