Shoulda left their asses glued to the wall.
I don't think the glue worked like they'd planned. Unless you have an accelerator, it takes time for the stuff to bond, and painted, porous materials like drywall are going to need the gel formula I would imagine.
CA glue, or Super Glue, can cure and bond almost instantly using an accelerator spray solution. I learned about that in woodworking videos, and now I don't use Super Glue without it! 10 seconds to bond versus 10s of minutes without moving the parts. If you move the two parts being joined before the glue sets, there's almost never a strong bond. You just get two halves with a hard, crusty layer of glue.
They must not have practiced before waltzing into the gallery with a tiny tube of glue each.
Maybe if they'd practiced, they would have opted for a more immediate joinery method -- like nail guns!
