There can't be anything damaged from 20 seconds of no oil, do you know how long it takes for oil to reach the top of an engine during cold start up? What happens when a oil pump fails, does the motor seize immediately? Does damage occur as soon as the failure? It takes time and heat with no lube to damage an engine, not 20 seconds of runtime.
Lets take a breath and get back to the original topic, do i need to prime the oil pump?