Re: Accidentally sent BTC to Bitmixer.io donation address but no refund
It's a hard lesson. Sorry for your loss, OP. Normally, there should be no reason for the Bitmixer guys being assholes, but if they decide to, there's little to nothing you can do. 
I'm sorry if this comes out as rude, but in Bitmixer's shoes, I'd do the same thing they did, and wouldn't feel guilty, or like I'm scamming you.
I'm sorry if this comes out as rude, but if I knew who you are, I would want nothing to do with you. You are the kind of person that delights in taking advantage of another's misfortune. If someone accidentally overpaid you, you would keep it. If a guest accidentally left something valuable at your house, you would keep it. If a friend (assuming you have one) accidentally disclosed a private key, you would spend all of their bitcoins. But you don't care because you are a guilt-free non-scamming scumbag asshole.
All of what you said is correct about me. Except the part about friends. Bitmixer.io were never his friends, pure business-to-client relationship. My conscience is very selective, and honest. You can trust me with any valuable goods of yours, and I would never steal or scam you, no matter what the situation, or the amount of funds. If me and you build a relationship of trust and good friendship, a mistake of yours just can't be handled that way, so my kindness kicks in. But "accidents" are unforgiveable in life. I learned the hard way, you probably yet have to face a situation like OP's, so your opinion will be like that, and it's expected to be that naive. There's a huge difference between being nice, and being fair, you need to know when you have to draw that line. You can't be nice to everyone, because not everyone will be nice to you.
Your trust rating does not seem to reflect that!
However, most of it seems made up (no reference links at all!)
And, this relates to the topic at hand. We don't really have any evidence that this transaction was ever made.