Well, I don't think anything fell in to your oil pan... I think it's pretty evident that someone installed the wrong cam!
No sweat though, it's not that big of a deal to keep running an electric pump for a while.
Heck, you might decide to install fuel injection, and the mechanical pump would end up being useless anyway!
You can get a plate to cover that hole, and leave the fuel pump off. That might help avoid confusion for someone in the future.
Have fun!
Edit: Like ag4ever mentioned, it would be a good idea to relocate that electric fuel pump.