The page is still there. I think it's was just overlooked, but as someone mentioned they couldn't message me on Booklikes, or find out how, I was curious. So I googled book likes and messages and this is the first thing that popped up.
If you click on that, you get to this:
Which should take you to your own messages page. You can get to the messages there.
Feel free to reblog this, so that people have an easy time finding their old messages and sending new messages, until it's fixed. (I assume it will be and soon.)
I'm going to send Booklikes an e-mail about this, too.