I sent several hundred dollars in USDT from my Bittrex account to Bitmex. The transfer did not go through. Bitmex says to contact Bittrex. Bittrex says they can't help.
Why would you do that? What made you think that Bitmex deals in USDT? They deal in BTC collateral only -- no altcoins of any kind. So I'm guessing that when they say to contact Bittrex, they are saying, "We're not going to help you."
Technically, the USDT is likely in Bitmex's possession, because USDT is sent between Bitcoin addresses. But most brokers and exchanges take the position that they won't recover currencies sent to the wrong address.
Here is what I got from Bittrex: "Unfortunately this is outside our realm of support, you will need to research how to remove a private key from a XBT address and import it into a USDT wallet to recover these coins. You will need to do the research as we can no longer be of any further assistance on this issue."
I have no idea on how to proceed from here. Has anyone ever dealt with this issue? How do I proceed to getting this resolved?
Am I supposed to ask Bitmex to remove the private key? If they agree to do that, then what is the next step?
If you sent USDT to your Bitmex deposit address, then technically they can dump the private key and recover it. But Bitmex is unlikely to have wallet support for it, and is thus unlikely to do anything for you. I hate to be the bearer of bad news, but you probably need to just take your loss and move on. Be glad that it was only a few hundred dollars. Next time, remember that you should only send BTC to your BTC deposit address.