Don’t dispare just yet. Your engine isn’t fatally destroyed, until it’s been confirmed destroyed and we aren’t anywhere near there yet. There’s plenty of things to check, before we declare your bearings toast and the reason for zero pressure.
When the engine ran for 30 seconds, was it noisey at all. If you had zero oil pressure or zero flow, the valve train would rattle like mad immediately, especially after sitting for more than a few hours and oil has had time to flow away from the valves, gears and chain, back into the sump. If the engine sounded relatively normal, you have at least some oil pressure and flow.
I would never rely on the factory oil pressure gauge. It’s a piece of garbage. You need to put on a real mechanical gauge to see what’s really going on.
It's possible that something got plugged near the oil filter, guage line. There is a bypass, as I understand it, so oil will still flow, but not necessarily show on the gauge or fill the oil filter. I would definately pull lower steel sheet pan and look at the pick up tube. I can't imagine it being broken, but plugged yes. If anything fell into the pan, including gasket material, it could have plugged the pick up.
I would check things in the following order….
Real mechanical gauge with the engine running. If no pressure and engine is rattling really bad, remove oil pan and check pick up tube for obstruction or coming loose. Pick up tube may still be attached, but loose, which not allow it to suck up any oil. If pick up tube is OK, then tear into the oil pump.
Just to give an example about not giving up or thinking the worst right away...I almost literally threw away a Honda CRX one time, when I thought I broke a belt and bent a bunch of valves due to the engine free spinning with the starter. Long story short, fuel had washed away oil ring seals, when I tried to start it with a bad distributor and after a few drops of oil into each cylinder, it started and ran fine. Car had sat for 6 months after I thought it was ruined as I figuring out who to call to tow it away and get rid of it.
Moral of the story is, don't make any hasty decisions until you know for sure what happened and what the problem and damage is. Check the obvious things first, starting from easiest to hardest.
