Do you know for a fact there was a merger or is my situation what happens when tribes merge?
The big problem is...no one is ever on. I'm on everyday and no one said anything to me about merging tribes. I have no idea where anything was taken, but half of the tames were mine before I joined that tribe and I also tamed more (some replacements, other additions) while in the tribe. I was, in fact, able to bust my way out because I was the owner of the wall above the door so I was able to destroy it and jump out. I also was able to punch a hole in the perimeter wall so I could get out. Then it was just a matter of requesting my tames to a small holdout I had built (I did that because people kept taking things off my character when I was offline). So I went from 18 tames down to 3. Yay me.
I know it's "just a game" but I pay money and spend real time doing things and it's utter BS that someone can screw up someone else's time/etc. like this.
The proper way for tribe merging to work is to actually be a feature...when the leader is invited to another tribe, all other tribe members should automatically follow. It's not hard to do; they already do it for base items with 'Owner: <whatever-tribe-name>.