you seem sure about this. How is that possible. i've sent before and after this transaction, all of them finished. The tx for this one has over 1200 confirmations and is about 24h old, and it doesn't show in pending balances on exchange. a few was stuck from the pool for an hour or so but this does not seem to be anything like that.
If a transaction has confirmations then it can't be in the mempool by definition. Mempool is where all the unconfirmed transactions are, waiting for their first confirmation. The only way to get help in your case is to contact the pool operator.