Don't know how accurate this is, but I've read that oil pressure switch for dash idiot light is set to 4 PSI. That is very low. My Jeep runs 60-65 PSI usually, and 20-40 PSI when at idle and normal running temperature. It never drops below 20. An oil pressure gauge is a very comforting mod.

 

OP maybe your filter was just clogged. Seems like it would have a "bypass" valve of some sort if it could not flow.

I agree. The Aeroforce gauges I use sit on top of the dash and have bright red LED warning lights that will come on at any pressure/temp set. No way to miss the warning even in sunlight. I set the low oil pressure warning at 25 psi. May not save the motor, but better than the stock setup. The other gauge is set to display tranny and coolant temps with warning thresholds set. Expensive gauges, but engines are not cheap either.

 

What most all eng oil filters have is a bypass valve. If the paper element gets plugged the valve opens, allowing unfiltered oil to flow.
Your eng oil probably did just drain back when u pulled the plug. As long as you have oil pressure, there shouldn't be a problem.

 

Thanks for the replies. It is something I'm gonna keep an eye on from now on. I may also try a new brand of oil filter like maybe the wix or just go back to the mobil 1.