Yup, there's still hope. Make a mixture of about a cup of warm water and a few drops of dish soap and put it in a spray bottle. Get out the hairdrier and warm up the stoneguard a section at a time, also turn on the lights to help keep the plastic warm. You will also need something to smooth/work the stoneguard. I recommend the soft plastic plaster/bondo scrapers (pictured below). Warm the stoneguard with your hairdryer and spray it with the mixture then slowly work it with scraper. Go slowly and carefully and keep the stoneguard warm. If you do decide to peel them off and try again, send me a pm and I'll post some extra pointers.

Oh, and you're right, I thought that other piece was for the horns.