I would give him some time to recover from the bullying. It may take a while for him to get fully back to normal, and that's ok. Don't punish him for it and be very gentle about it. It's great that you made the bullying stop. It's up to us parents to stand up for our kids when they can't. Even though it has stopped I would go the next step and get him a counselor or therapist to help sort through his feelings. At 6 he probably doesn't really understand what happened and is having a hard time processing it.
Two things still come to mind. Is he a deep sleeper? He may only be partly waking up in order to head to the bathroom and be sort of dreaming he is there. I have heard of other children doing that. And perhaps he just can't hold it long enough to make it all the way. If he is half asleep that would really explain the lack of memory.
Way to go mom on being so involved in what is happening at school and dealing with the bullying. Also great to hear that there is zero tolerance. Still, if he is feeling lonely that can be almost as bad as the bullying. So I wonder about friends. Does he seem to have kids he plays with?
I still highly doubt this is intentional. I think I would take him to the Dr. and discuss there first. Best of luck.
I have thought about the possibilty of it being sleepwalking, but have no idea of how to go about stopping it, I know kids can go through phases of sleeping walking, but I haven't heard of people urinating whilst doing it. I was bullied at school myself, so I fully understand how he feels, and I have a very active role with his school about dealing with it. His school is only small (250 students), and the children are monitored closely, but even some kids slip past the teachers behaviour wise, when they are dealing with other kids. The good thing is that his school has a zero tolerance on bullying, and the punishment these kids have received, has certainly stopped them from doing it again, my son has been told by the teaching staff to stick to areas that are constantly monitored by staff, to prevent it happening again, and I always take over the monitoring part from the school gate to our car. My son isn't one for opening up, but if you do it right you can get everything out of him, without him even realising it, but when it comes to this urination problem, no matter what tactics I use he wont open up.
I agree with adgal about both the possibility of sleepwalking and about either continuing to be bullied or simply having been ostracized for being a "tattletale" about the bullying. I'd take the bullying possibility very seriously, there have been some pretty tragic occurrences lately. Who really thinks the kids involved will tell the adults who are supposed to be watching the situation everything? Not me. Any possibility of changing schools?
You know, I know it's not super common, but I have to wonder if he is not sleep walking a bit? A lot of young children still pee the bed at this age, so it makes me wonder if this is not a version of that? He thinks he is in the bathroom but in such a deep sleep he doesn't realize it? Also, if he has been a victim of bullying, just because the bullying has stopped now doesn't meant the fear has gone away for him.
First off, I don't think I would punish him for any of this behavior. He is still so young, and I doubt he is doing this just to misbehave. I think I would probably consult a specialist along with his Dr. I would first find out if there was any medical reason for this (ie: he is in a deep sleep and can't quite make it to the bathroom in time), and then I would talk to a child behavior specialist to try to get to the root of things (perhaps the bullying hasn't completely stopped, or he feels ostrasized by other kids). Just my two cents. Whatever you decide, I wish you well.