Hard to say whether you should or shouldn't...
I guess I'm not in your shoes but if I were in a similar situation I'd probably say it like it is. I'm not the type to walk away though... At the same time if you're somewhat ambivalent about leaving or staying I think it is risk free for you to allow yourself to come forward and may be even confront the supervisor. If he's got any balls at all he'll respect you for it. If not... he might just get his knickers in a twist... But I guess if you're leaving it won't matter one way or the other.

I know it sounds somewhat macho but sometimes you just have to do what works.

At the same time, if you've thought about this a million times and decided to just cut losses (if any ensue) and move on that is also understandable. Some things just aren't worth wasting your time on.

-ED-