"Ghost" app in app drawer

I've run in to a very odd problem with my Acro S running 6.2.B.1.96 (deodexed).

I've recently noticed a blank space at the top left of the first page of my app drawer. This is with the app drawer sorted alphabetically which is how I normally have it. If I choose one of the other orderings the blank space still appears, but in a different place. For example, sorting by "Most used" it appears about half way through, after an app which I know last used back in mid-June. On the other hand, sorting by "Recently installed" it appears before an app which I know I installed only the other week.

I can't run the app by tapping on it in the app drawer - nothing happens. But if I long-press on the empty space then the "Add to Home screen" panel drops down from the top of the screen and I can drag the invisible app and drop it on to the Home screen (I can even drop it on top of another app to create a folder!) I can't run the app from the Home screen either, but if I press and hold on the place where I dropped it then the trashcan pops up at the bottom of the screen and I can drop the invisible app in there to remove it from the Home screen.

If, in the app drawer, I select "Uninstall" from the menu, no little red cross appears in the space occupied by the invisible app, so I can't get rid of it that way.

I've installed & run Malwarebytes and AVG antivirus and neither of them have flagged anything which could be causing this.

Does anyone have any ideas about how I can go about establishinig the identity of this mystery app, and either making it visible or uninstalling it?

It's an official build, been on there since last August. The ghost app only showed up in the last week.

I've tried recovering from a nandroid I took about a month back. I first tried doing just a restore of system, but the ghost app was still there. After a full restore the ghost app was gone. However, I am now having issues getting contacts to work- it simply reports "Unfortunately, Contacts has stopped" - so I may have to recover back to the nandroid I took this morning before I did the restore and then maybe start all over again. Sigh...

Well I got rid of it in the end, but it was a tortuous process. I restored a system backup (nandroid) made about a month ago, then recovered data for apps that keep it locally from the latest Titanium backup (which runs every night). E-mail & contacts restored automatically from the cloud. I then had to carefully update every outdated app, checking the app drawer each time to see if the ghost reappeared. It never did. I still don't have any explanation for what actually caused it in the first place. Quite frustrating, and very boring!