Did you by any chance have an external hard disk or some other backup media attached when you did the update?
I have noticed a strange quirk with iPhoto and iMovie. When I have my backup hard drive installed, and I do a software update, the software update will update iPhoto or iMovie *on my backup drive* but not on the system I'm booted from! It will then update the receipt on the system I'm booted from. Result: I can't update the copy on the local hard drive!
I've seen this happen twice now. So if I have the external hard drive connected when I do an update, sometimes I have to copy the updated file from the external hard drive to the internal.
I've also seen this happen with a very small handful of other apps I got from the App Store (namely, Better Rename and Picturesque), but most apps don't do that.
