Please be careful out there. I lost 2.2 BTC because of them. Everything looks fine until they send they send the coins to the different address than specified. You get your "Letter of confirmation" but the address on there is wrong. Not sure what happened because I used them before and it was fine, perhaps they're only interested in higher amounts :/
bitmixer.io doesn't exist anymore... [scam]bitmÃxer.io[scam] does... so yes you have been scammed.
edit: or at least it's not the same site, I can't be sure they are scammers since I've never used them.