[stomachmonkey]

Cats are "generally" pretty reliable about using the litter box.

If they are sick or the litter box is not kept clean, (which might be the case here considering how she left the place) they will find other spots.

Black lights kind of work.

Check carpeted areas first.

If it's old pee you can get on all fours and you should be able to locate the spot or spots with just your nose. You don't need to stick your face in the carpet.

They'll also find an out of the way corner possibly in a closet. That can be more problematic than carpet. If they make a puddle in a corner it can leech under molding and wick into the drywall. You can try KILZ on that but really the right way is to cut out the section and patch it. Also replace insulation if there is any behind it.

If the carpeting is soiled your cheapest / easiest / surest way to deal with it is get some nice commercial grade cheap carpet from Home Depot / LOWEs and be done with it.

EDIT: Don't forget, cats do spray, especially males so you may be dealing with a vertical surface, wall, cabinet, etc... and not the floor.