...so if you shine a light up through those holes, you don't see any threads? Double... no... tripple check that. It's possible that when that mount was replaced, that they didn't replace them with the right fasteners... so the ones you have may be too small. The nuts on mine are welded inside an area where you have no access... so I'd imagine there's no way any other mechanic could have removed them, and it's too young of a car for them to be rusted out.

Reflecting on how my lower mount is connected while I was swapping my motor, I can't imagine any way for this to be possible. I'm trying.