fixing leaking rear main seal

Are you sure it's the rear main leaking? An idle leak (leak when it's sitting) generally isn't the rear main. The rear main usually only leaks when the engine is running. Idle leaks are generally either the pan, valve covers leaking down the back of the engine, or the oil filter adapter leaking.

Anything is possible but I doubt it stuck to the crank enough to cause it to spin when started cause the area of contact on the crank is very small in comparison to the area of contact to the block and cap.