Mike, coming on here and threatening the people who stole these items with the closure of the vendor hall is as effective as the cops going on TV and asking a bank robber to turn himself in.
But, I know with 100% certainty that the Westin has security cameras ALL over the place...if not IN that room, then in the halls around that room. When you asked their security director to see the video from the time and areas in question, what did he tell you?
Last, I don't see this as a "Big" problem at all. If the vendors that had these things stolen want you to make it right, and you think it is either your responsibility or just "good business" to do so, send them a check for $500 each. That is a small fraction of the gross, and this laundry wouldn't be airing out here.