I am noticing that some messages appear to have vanished over the last few hours. I can only assume that Trip Advisor is working behind the scenes on something and they will probably reappear in a while.
It appears to be some of the regional boards that are affected. If you can't find your message looking in the area where you see all the boards together then you can try looking just at the area board you posted on. However I find messages missing from those areas also.
I think the best thing to do is to go to your settings and find the list of contributions you have made. As far as I can tell the messages still appear there and you can check to see if your questions have been answered that way.
Just be aware that some of the people here who are great at answering questions may have missed your question because of this glitch so keep checking back for more answers over the next couple of days or until the system rights itself. :)