Axolotl despawns after catching it with a bucket and releasing it

Hi - I caught an axolotl with a bucket and brought it home. I released it in a pool that I made. I went to get a nametag and by the time I came back (less than a minute) it was gone. Per the wiki, if they are caught with a bucket and released, they shouldn't despawn. 

"Axolotls picked up with a bucket and re-spawned do not despawn."