I'd discourage OP if he wants to do this, regardless of how much BTC he lost. The time and money spent to get his money back is probably not worth the hassle. Just move on OP, and learn from this to never share your private key with others, even if they are famous/reputable in the community. Some services even straight-up exit scammed you when they believe they are being threatened or they no longer make profits. It takes a single take-down notice or insolvency notice to lose all of your money, better store all of your crypto in a secure wallet next time. At the end of the day, this is one of those risks that you need to accept if you used a service that works like Chipmixer.