Good to hear you have it running again. Did you determine if it stopped due to low oil pressure or the fuel pump switch?

Hmm, If there's combustion gasses leaking from the rear seal you'd think the rear seal would be spewing oil. Oil pan surface is on the same level as the crank maybe combustion gasses leaking from pan?

Plugged, wrong, no PCV valve?

Maybe a vacuum line bleeding (filling) after shutdown, do you have an automatic transmission?

Maybe air pocket in the water jacket or heater hose steaming off?

Oil draining back into the pan?

Combustion gasses in the cooling system?