Thank goodness this doesn't happen often, but it happened to me recently. I had my full day Electronic Marketing camp scheduled for a 7:00 AM setup with attendees to show up around 8:30 AM. I showed up in the room and no one was to be found anywhere.
Here's a checklist of what to do:
1. Immediately use the house phone to call the front desk and ask for the "manager on duty." Start raising a little h _ _ _. I do this simply to get their attention. You might mention something like "breach of contract" which usually gets extra attention.
2. Start opening side doors in the meeting rooms and looking at all the other meeting rooms to see what you can scrounge, tables, extension cords, chairs, etc. Drag them into your meeting room so you can take ownership. (I'm not saying ruin someone else's setup, I'm just saying if no one else's room is set up, then it's their fault if they didn't come down to double check things early so grab what you can.)
3. If you need a screen and none has shown up, (this also happened this weekend) find the most usable section of a white or light colored wall and set the room around that area.
4. If you have a breakfast scheduled or coffee/tea service go directly into the kitchen and start yelling "HELLO." Always have a copy of your contract with you if you have one. Go directly to the chef on duty and see if they can get something going quickly.
5. Don't be afraid to jump in and do things yourself. Move quickly with a stern look on your face. If someone eventually does show up, this demeanor should transmit the idea that you are miffed and there is not time to play games.
Yes, I know some people will say that you should be sickening sweet to get things done, but I'm afraid that when there are deadline time constraints you must get action quickly and many hotel staff people are not in any kind of hurry, so if you want to be ready when those attendees roll in, you have to move people to action.
Oh, one last thing. Always have cash bribes on you to get fast action when you really need it.