if at fault for a fender bender, there were no injuries or damage to other car, if i was to not contact insurance company what would happen?

Unless the other party called the police or notified his or your insurance company, nothing would happen. Your car would simply remain damaged.

But......Since ONLY insurance companies can determine fault and you have not notified your insurance company of the "fender bender" how can you possibly know that you were at fault?

The gene pool is getting very shallow

if you exchanged insurance, or information, it should be fine, but its foolish not to tell if you were at fault.

If the police was involved there is a record, if the other people took pictures of your license plate, they more than likely will come after you anyways. hopefully you took pictures of them too.