This happened to me. I have a friend that races with me and works in a machine shop and was able to get it out. The screw was not deep enough to allow another screw nor out enough to dremel it with a disk.

I am not sure what method he used to remove the screw, I know it was just possible to. You might have a chance to take it to a machine shop and they might know what to do.

I also recommend to fill all holes in the crankcase with cloth so no debris enter the bearings.