It's like those stories you read about museum janitors cleaning up a mess in a room, only to discover the mess was an "installation," and they just demolished a work of art:

It's worth a lot of money because it's a Banksy, and because Banksy is elusive. If i was any ordinary tagger, the owners would be annoyed. The billboard was probably taken down by CBS for two reasons: 1) it's good customer relations to repair work that's been damaged by vandals, and 2) Disney might not look kindly on Mickey groping a model.