It's been 2 days already. It is probably a scam. There is still a chance that OP may come back but the chances are not favorable here. Even if they do come back, 3 days just to mix your coins with no support and a scare at best case scenario is not what I would want as service when I'm just trying to anonymize my coins. Nor is it "convenient" in any means at all.

The "admin approval" thing could prove to be a threshold at which they will not automatically give you their coins and selectively scam you.

Tryninja is completely spot on. There is no reason for smartmix, a mixing service with no background or reviews to appear second on a review website. Either the site is bogus, or the service has probably paid for them to be on there.

Good to hear that you've learned your lesson, you should open a scam accusation within 2 days if they do not refund you so that they can get tagged as well. Also, I do hope that 2 BTC isn't a big amount for you, cause it would be devastating if I got scammed for 2 BTC for sure.