I have just read the thread. What happened is that you sent money to @poloniex without using the correct memo ( unique identifier), without this memo poloniex don't know where to credit the money.

here is the page to deposit money to poloniex https://poloniex.com/balances

can you read what it says ? It says You MUST send your deposit using the unique Memo above. Failure to do so may result in the loss of your deposit.

You can try to contact them here https://poloniex.freshdesk.com/support/home and try to get your steem credited but as the warning says it may result in the loss of your deposit