So after checking my wild 2* wolf... yeah it despawned. No idea why they programmed them like that, for your tame 2* wolf?, i got some bad news.

https://www.gosunoob.com/valheim/2-star-wolves-find-tame/

Even tamed 2* tamed wolves despawn, you need to breed it, get a 2* pup, that one will NOT despawn. I mean, who designed this.