I have read the thread and someone mentioned "abandon transaction" (post link),
And he might have removed the transaction from his mempool so that he can create another one using the same inputs.

So by doing so, he effectively double-spent his original low-fee transaction that caused it to be dropped - the new transaction have a different hash/TXID.
In Bitcoin, we have a double-spend protection like: nodes' mempool will reject any transactions that re-used an input already used by any of the previous transactions it received;
except if there's an "RBF flag".

Other ways to get a transaction dropped is to wait for the default transaction expiration of 14-days.
It it wasn't mined after 14-days (starting from the time it was received by the node), the transaction will be dropped.

Take note that Altcoins have different network rules than Bitcoin.