Mark,

A pushrod that comes out of its proper location isn't a common occurrence. It can be an indicator of other problems. If the pushrod is dead straight, I would loosen the companion rocker arm and stick it back where it belongs. It's important to make sure the end in the lifter is really where it belongs.

Bring the rocker arm back where it belongs and adjust it properly. Keep an eye and ear out for any further developments...it, contrary to your machinists statement, isn't common to have this happen. That's how I see it.

Stuart