What dragonyphoenix already said - in the show it seemed like anything that's put inside the vampire goes poof.
Everything else could be subjest of scientific experiment...
Like, if you put several vamps around an object, so they enclose it, would that objesct disappear when you kill the vamps?
Or if you dismember and slice the vamp in a very gruesome but non-lethal manner, so vampire's flesh encloses an object... (Yikes, I know.)