Don't let this one shotty experience with a scorp ruin it for you man, they are far too awesome! Your humidity was fine, your temp was fine, and your substrate was fine. Thus, it wasn't your fault! Like others have said if there was a hole in his tail, it couldn't have been self-inflicted, so it was most likely a parasite. I'm guessing the guy who sold it to you either had his scorps in horrendous conditions, or it was wild-caught. Check out Kenthebugguy.com, he usually has great deals on scorpions and a great selection. I think your best bet would be the desert hairy, flat rock, or another emp. Good luck bro!