I don't know if this is a bug or not, but I just bought 2 wolf eggs and 2 ocelot eggs and I placed them in a fenced in area, I left the area for a few minutes closing the door, and they seem to have vanished? This is the second time the ocelots disappeared, but the first time for the wolf.
Same thing happened to my dog a while back... it was named St. Bernard. Not sure if its the same glitch but the spooky egg I just spawned yesterday seemed to disappear too. (yes ik the mob is invisible, but the egg it was wearing sure wasn't.)
It was in a closed off room too with no way of possibly getting out. There goes 20k down the drain...
Baby wolves and ocelots seem to despawn if they are not tamed. Make sure you let them grow up and tame or egg them before leaving the chunks. I have had this happen before and someone told me that this is what happens.