Yes, I also found this tread meanwile and posted a response to the OP asking how the situation turned out for him.
He hasn't logged into this forum since September so I guess he won't reply any time soon.
In the meantime I am waiting for Poloniex's response to the ticket I opened yesterday.
Please let us know about the latest status of your case. Not accepting a Tx after 100 confirmations is very unusual.
The address that they sent it to was for a USDT wallet, not a BTC wallet. So I am sure that it has been sent and is sitting in at the BTC address with the same address as the USDT one used. Maybe I'm wrong but I'm pretty sure they are two different blockchains. So the coin is sitting on the BTC blockchain at the address sent to. The USDT address will not see the coin because it was broadcast and sent on the BTC chain, not the USDT chain. And since I'm sure no one has the private key for that BTC address, then the coin is essential inaccessible and might as well be considered gone.