Just a wild guess, but there was a report of a Caylee sighting on AirTran Flight 862 (Orlando to Atlanta). That could have been enough. Or maybe the local LE asked for assistance.
If Baez didn’t try to get a plea deal for his client, just another reason to have the guy’s license yanked. But Casey Anthony strikes me as the type who’d refuse a deal, certain she could pull one over a jury.