Missing Discs

We regularly remove and replace discs from our two changers. Because CDJ doesn't automatically reupload the memo text, and group information to the player, we put them back in the slots they came out of. The trouble is that CDJ doesn't make it easy to do that. Once it discovers that a disc is missing, it sets the player and disc fields of the database to -1. It would be nice if it retained that information and indicated the missing disc some other way ("Location Valid" field maybe?). I would have suggested negative player and disc numbers but the player is 0-based.

Anyway, a real nice feature would be to get a list of missing discs and what slots they're supposed to be in. I was going to do a query within Access for this but couldn't figure a good way to do that.