Amazingly i drove dads old au 5ltr around 20 - 30 minutes with little to no oil in it. turns out the oil pressure sender died somehow making the oil guage just freeze and being on the highway with the stereo up didnt help matters. wasnt till i got off the highway that i heard the horrific noises. checked the dipstick no oil. The next day dad replaced the sender and refilled it with oil and it runs fine
Just because there is no oil on the dipstick, doesn't mean there is no oil in it. Not all dipsticks go right to the bottom of the sump lol
I've heard of some old diesel engines getting away with this, but I think in your case, there might have still been oil at the pickup, hence the engine running for half an hour and living still lol
