Can you cover it with /abm count all?
The "/abm count all" counts all of your animals, but does not provide a "grand total", just totals for each animal type.
If an animal is really lost, i.e. is dead/ killed, then it is automatically removed from the list. This "dead animal watcher" is active every 20 seconds.
I would like to say that at the latest after 20 seconds the "/abm list all" should be actual.
For some of our players with many (50+) animals (building zoos), there are animals that they never seem to be able to find (after even minutes of doing /abm list commands) and they stay on their list. Would it be hard to have a command like "/abm release cow 25" where the number is the number listed in the /abm list cow listing? This is an example for just cows, but have for all animals?