FWIW, you're the first case that I've heard where the DIF directions were followed to the 'T' and you had a disaster. Hopefully, as the disaster 'unfolded', you stopped and only did minimal damage.
In any event, bathroom wallpaper is usually a vinyl product because, well, if it was paper, it would get ruined very quickly due to the high humidity from showers and such. After you're finished doing the demolition and repair, be sure to use a good primer like Latex Stain Kilz before you do any painting or wall papering. Again, due to high humidity, you need to protect the walls.
Question: What 'type' of wallpaper was it? And did you use a paper tiger? (I've removed wallpaper from all kinds of rooms in all kinds of homes and have never had a problem. Keeping the water boiling hot and letting the DIF solution soak the walls for the 2 15-minute intervals were the key. Can you say more???)