gotta pick it up, I don't think just because someone saw you picking it up they would blame you, anyway. Especially if you explained you're a fellow motorcyclist. Furthermore in nyc more than likely you'd be walking by and people on foot don't knock over bikes, cars and trucks do. In any case, I don't think that way.
I've found my bike(s) both lying on the ground and having been picked up after being knocked over. Let me tell you that I was much more angry finding it lying on the ground
I would also think about leaving a note saying that I didn't see who did it but I picked up the bike and sorry that it happened. Might make the guy feel better.
