So I took my bike out of its shipping box and went to reassemble it, and the derailleur hanger is rocking. What?

Somehow, the threads of one of the mounting bolts got stripped. I have to assume it's been loose for a while and just rattled around until the threads stripped themselves out. I've never had it off. It's been straightened at least once.

Should I worry about the frame or anything else, or just replace the hanger? I don't see any sign of frame damage, and I did have the LBS check it out after my crash in '10.