I'm not entirely sure how the rocker came off, but it was actually jammed into the side of the cylinder head. I had to use a screwdriver to pry it loose, and you can see where the rocker had embedded itself in the head. Would explain some of the noise I heard, but not the engine stalling after a few seconds. Does the ECU kill the engine if it detects too much knock from the knock sensor?

1995 Montero SR
2" Body Lift
35x12.50x15 Cooper Discoverer STT
Aisins