Oh gosh! You mentioning your mattress reminds me of what my black lab did to my moms bed lol
She had a water bed, one with the tubes and the foam between the top lining and the tubes. One day we left for somewhere (don;t know where it was almost 10 years ago) When we came back, the foam was completely gone! He ate it, not a sign of it anywhere *sign* that was the last straw for my mom. Ended up having to find a home for him
He had chewed and swallowed.. toys, clothes, stuff animals, ice (his favorite haha), his plastic food bowl (ended up switching to medal and he tried chewing those) and everything else in the house.
Back then I was a noobie when it came to dog training, so I had no idea how to correct that, and my mom had a disorder that ate up her energy, so she didn't have much time for that after working.