Just out of curiosity - have you seen Gargamel using his hides after you added the sphagnum moss? Some snakes don't mind the moss at all, or might even like it, but I know my boy Iggy objected to it pretty strongly, lol.
I was trying to ensure a good shed so I added some slightly damp (not soggy) terrarium moss to line the bottom of his favorite hide, which is one of those little enclosed rock caves. He started slithering into it, and I saw the exact moment he stopped short, decided he didn't like the smell, and U-turned right back outta there. Gave him some time to get used to the change and give it another chance, and he just wasn't having it. I then removed the moss, but since some of the smell still lingered, he went into the hide and then came back out again after just a few seconds. Finally, I thoroughly washed the hide so there was no smell remaining, and he deemed this acceptable, went back in immediately, and stayed.