oil pressure

[LasVegas]

I took the mall queen for its first offroad experience yesterday and had a blast...until about noon. We started out on the trails at 9:00 am and everything was running beautiful. About noon we pulled over for a break, shut it off and got out. 20 minutes later got in, started it, and got chime alarm and looked down...-0- oil pressure. Immediately shut down but the engine had sounded fine with not even lifter noise which proves there was pressure when I shut down earlier. Checked oil, full and clean. Okay, it's that sender or gauge problem and it finally failed, right?. Wrong! Restarted, same thing except now lifter noise starting. No doubt, -0- oil pressure. Now we're in the mountains on the California/Nevada line, no cell or Onstar service. The team did a wonderful job towing me to the closest (30 miles) one bldg "town" where we arrange a flat bed to Vegas. Thanks guys. It's now at the dealer waiting for them to open tomorrow & I lost a nights sleep. I've racked my brain on this and without engine knocking or other sounds I don't think it's bearings or internal engine problem. Oil pumps rarely fail at 16,000 miles and the only thing I can think of that would cause this kind of sudden oil pressure failure is the oil pressure regulator (a ball & spring) within the oil pump. If the spring failed (broke) I believe it would cause -0- psi. For those that understand internal engine workings I'd appreciate your thoughts. HummerTech or anyone else ...you have any ideas?