Well, I found MY problem. The message WAS showing up, it was just hidden underneath some other stuff. The main problem was that the client had wanted a "read more" thingie on every single page (ugh) and so the developer who wrote the theme had to calculate the div's height when you expand it, and the error message div wasn't there yet, so it didn't have room to show.
I made it so that page didn't do the "read more" thing, so that solved it for me. Another option would have been moving the error displaying div with css.