Originally Posted by
eeuuugh
The crimps do look about the size of the Efficient Velo Tools "right arm repair clamp", which is something I'd expect a better shop in the Northwest to have, and can very easily be tightened too hard.
This ^^^. Did you look at the equipment they use to hold work there? Looks like poorly-adjusted repair stand clamp damage to me -- something pinching, not metal, and yet with leverage. I think that if you are sure this damage did not exist the night before, you can see anything in the shop that looks like it might have caused this, and threaten to get a lawyer, you'll probably get somewhere. Whoever did that just ruined a vintage seat tube, in a hurry. And that's what probably caused it: being in a hurry rather than taking appropriate care. It will be quite expensive to fix and repaint.
You could also have someone expert dust the bike for fingerprints. That might tell you something about who is personally responsible.