Patch 5.3: Known issue with pet licenses
Community manager Nethaera hit the official forums this afternoon to notify players of a known display issue with pet collections. The notice reads as follows:
In other words, while your pet pane may display that you're missing some pets you've previously acquired, they haven't actually been lost. By the time you read this, the issue may even have been resolved already. In either case, don't panic: your pets will return soon.