I know I reported this in the How do I, through much confusion a while back. And It was determined that my animals were most likely aggro'd from outside of my walls. This caused them to Unhitch and Despawn. However Since then it has been changed so that animals cannot be aggro'd through walls fences. Also with the expansion of my base, the area my animals are taming at, is no longer accessable or viewable from outside of my walls. Another player or animal interfering here is not possible.
Here's what happened. In my little pen I 6 Taming posts, very uncleanly placed. As well as a food trough. The fence has one hole in it, being covered with a wicker basket. Within my pen I had 1 Tamed Female Cow, 1 Tamed Male Cow, 1 Tamed Sheep (Gender Unknown due to lack of frame of reference) 1 Muflon that has gone through a couple taming cycles. 2 Aurochs that I am pretty sure I've missed the Taming window for a couple times. I have been managing inventories, and crops for the past 8 hours in my base, and have been paying close attention to my animals, looking for any that are ready to fight. Within these 8 hours nothing has entered that stance. I went mining. came back and both of my Aurochs were missing. I was only away from my base for about an hour.
They were there when I logged in 9 hours ago. I have fought no animals since then, so I must assumed they were correctly hitched when I logged in, or they would have not been there when I logged in.
I also must conclude that it cannot be due to missing a taming cycle, because if missing X Taming cycles caused them to despawn, then wouldnt they despawn immediately after a taming cycle ended? not 9 hours into the wait for the next ready to fight stance.
I understand this is not a lot of informatin to go on, but I plan on trying to tame more Aurochs, and possibly Muflon depending on the second one I'm tamings determined gender. So I would be willing to troubleshoot a little if there are any idea's floating around.
Let me know if you need/want more information.
(Edit: I did sheer my sheep in this time period. I also attempted to bucket my tamed cows to see if any milk was available. I also tried to bucket the aurochs getting no milk.)