On Friday, Tweet Scan's main database server crashed. I've spent the weekend rebuilding it and getting the backups restored. Unfortunately those backups were missing some data so all tweets from Feb 1st, 2009 to March 29th, 2009 have disappeared into the ether. That's about 2 months or 10% of the database.
The good news is, the service is now up and running 100%. Daily and weekly email alerts are back and operations are being improved so this doesn't happen again. Thanks for your patience and happy scanning!