The problem with bumping into him like this is that it could spark things off in his mind again.
It's a year since I saw my ex-girlfriend, but I know if I bump into her again, it will start her off trying to hound me, find out where I live etc. like it always has done in the past.
I hope that doesnn't happen, but a small thing like last night plays on the mind of nutters like that, so just be safe but also, dont worry about it too much, you've obviously got the experience to deal with it, and have done the right things in the past.