Well that's a bit of a predicament!
I'm a little confused about the details of the problem though.
the edges for the screw appear gone.
— what exactly is missing? The incisions in the head? The threading on the shaft? The helix on the inside of the hole?
If it's a problem with the screw, maybe you can borrow a screw from another virtual pet that you're not using right now. (Idea inspired by this post
If it's a problem with the hole — well, duct tape isn't so bad is it?