Dazadoop
Newcomer
It's happened to me a couple times now. First with the sleep shack and now again with the bridge by the archeology tent.
When I talk to the parrot by the shack it still offers to build a mailbox so the game must still be recognizing that I restored the shack??
I don't know how to fix this and I'm afraid to spend anymore walnuts on building things if they're just going to disappear overnight..