If the engine was not put under a load or accelerated above idle, he might have dodged a bullet. Try pulling the distributor and repeating the oil pump spin. If there's proper oil flow, the drill motor running the pump should load down noticeably, enough to make the drill hard to hang onto. It's possible the pump drive shaft has failed, or the distributor might not have been seated into the shaft correctly. I've also seen a new oil pump fail to prime itself if it's not packed with vaseline or oiled before installation. Bottom line- - - -at least pull the oil pan and inspect the bearings. If the crankshaft isn't scored, it might be a good idea to change the rod bearings. Mains are usually pretty durable, unless the engine is under load when the oil pressure goes away.
God luck!
Jerry
