Yesterday I just created a 2h recording using the standard Apple's Voice Memo and "imported" seamlessly to my Mac, no issues at all. It went to my music library in an album "Voice Memos".
I can only say there's nothing special that should cause such an issue and I confirmed it. What I would do in your case is checking the Console hoping for some informative warning and trying to record another file and see how that goes.
But there's a good chance you've got it and is just not finding it, like other dudes. Worst case scenario, get iPhone Explorer and grab them manually. There are some steps you might want to follow and see if it helps in you case. The first one is: Restart you mac.