That sounds really horrid. I would have thought if it was any wild animal they would have eaten it. (Although they may have been disturbed – but why didn’t they carry at least part of it away.) It doesn’t sound like a fox – I believe they wait until the hog unrolls and then attack the soft part. (sorry to be a bit graphic) I suppose it could be a domestic dog, but I wouldn’t have thought they would decapitate it. It might be worth getting it looked at by the RSPCA, in case. Although it would obviously be better if they had the actual evidence rather than a photograph.
Re. problems logging in, changing password, etc. If you go to ‘My Hedgehog Street’ above and click on ‘Accessing the new website: troubleshooting’ it tells you how to change your password. If you want to put a photo on you can put it in the gallery, but that sometimes takes a while to appear. Otherwise, if you don’t have photos elsewhere on the internet, the only thing you can do is put a photo on as your profile pic. You can change it again quite easily and quickly. I have changed mine several times. I can understand that you may not want to put this particular photo on as a profile pic, even for a short time.