Wow, that is very, very odd. I remember back in OOTP3 I had a player retire and show up on my roster before using default roster sets. (It was Mark Grace, and since he was still good, it didn't really bother me.) According to some it sounded like the duplicated player bug, but I didn't think it could be since I was using default OOTP3 rosters.
Not that that had ANYTHING to do with your problem.
But I haven't seen anything like that in OOTP4, although I don't sim historically.