Any idea what kind of engine is in this vehicle
Lots of things can cause it - but, since you didn't hear horrendous noises following the departure of the pressure ... I would doubt it's a major mechanical failure at this point.
1st would be to confirm the actual galley pressure via a test gauge hooked into one of the direct oil pressure ports.
At that point - if any pressure or really none at all - you will know what has to be done next;
* fix monitoring system (gauge, light et.all)
* remove distributor to check pump drive shaft and connection
* pull pan to check internals
I would doubt the pump drive shaft, from the bottom of distributor to the pump, has 'broken' - unless you have a modified high pressure/high volume pump that is (was) really stressing the link.
More likely would be the pump has fallen off (it happens more often than you'd think
), the pump body itself has failed (common with poor quality replacement units) or ... the oil pump Pick-up assembly has just fallen off the pump body.
If the pick-up was not secured to the pump body they will often 'wiggle' or vibrate out of the pump and fall into the bottom of pan.
I'd run the engine as little as possible until you confirm what the cause is ...