I assume you've already tried rebooting the phone. I've found this is the easiest thing to do to get tracker back on its feet regarding added/deleted pics like when I save email and MMS attachments . . .

. . . Unless, of course, the all the tags ever applied are stored in a config file somewhere and never deleted . . . I grepped "tag" recursively from /home/user dir and quickly realized that that wasn't gonna get me anywhere.