Well, it might not be as bit a deal as the thread title alludes to, but last night (why didn't I just go to sleep?), I adjusted the truss rod on my American Standard and now the walnut plug is protruding out of its hole. Earlier in the day, I lowered the micro-tilt so that it is no longer shimming the neck and just wanted the get the action a little lower. It seems that the rod is functioning properly and I didn't feel anything unusual while I was adjusting it. Can I just tap it back in or should I have a pro look it?

You can just tap it back in. If it pops out again, give it a tiny dot of wood glue to secure it in place.

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Before you can tap it in, you will have to tighten the truss rod a bit to make room for the plug. Loosening the truss rod to the point that you engage the bi-flex feature, can sometimes put so much force against the plug that it busts loose. Go ahead and tighten the rod back up snug, dab some good wood glue (like Titebond) around the plug, then tap it back in to flush. Wipe away the excess glue and allow it to fully dry before loosening the truss rod or loosening it to the point the bi-flex adjustment begins to put pressure on it again. Of course, if you bought it new, you have the lifetime warranty, and I would go that route rather than void the warranty with an at-home repair

It is normal , sometimes , that the plug go out.
The truss rod push it. Truss rod need this room. Try to tap in place. Do not glue your plug. Truss rod won't work easely after.
Maybe you can try to remove plug and sand it shorter ?

It's fine now. I just tapped it in without any adjustment to the road and it went back in easily.

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