yeah, same happened to me when I tried to send BTC to my account at Poloniex. It actually never arrived there ... somehow, after 3 days it returned to my wallet... I also tried to purchase an online course and pay for it with BTC... interestingly he same happened, first my BTC got stuck with 200k other transactions..then I got an email from the BTC pay platform that my BTC is stuck, then the sent me another email that I can claim a refund...which I did.. and then I got a conformation from the course, that they received the payment and I'm in the course ... :O.. good deal, as far as I'm concerned :)