I recently upgraded to Lion and tried to migrate my Time Machine backup. Then I couldn't find my files.
I recently upgraded to Lion, then bought a new Mac which had Snow Leopard installed by default. I tried to migrate my Time Machine backup to the new Mac. First I had to upgrade the OS to Lion since the TM backup was created using Lion. Once the upgrade was complete and I tried to migrate my data from TM, I couldn't find my files.
I looked in System Profiler which said I had 95gigs of movies, 48gigs of music and so on. But none of these files could be found in my system. I discovered that when migrating TM data, Lion creates a new user account.
Then when you first log in, the account is fresh and clean with no data. If you go up to the menu bar and look for your mac account name on the right, click it. You'll notice another account along with the 'Guest' user account. Click on the other admin account and log in. There is your Mac just as you left it before upgrading.
[crarko adds: I don't have a setup to try this, but in the past I remember Time Machine prompting about what to do if an account with the same user shortname already exists on the target machine. Maybe that's why the new account is now created? Anyway, if someone else has had to do this please post how it worked for you in the comments.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20110808123327704