I have read the thread and saw someone mentioned "
abandon transaction" (
post link),
He might have removed the transaction from his mempool so that he can create another one using the same inputs.
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: most 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".
Or it wan't propagated in the first place for some reason (
eg. non-standard),
it's just sitting in his own mempool that's why it didn't appeared in any blockexplorer.
Other ways to get a transaction dropped is to wait for the default transaction expiration of 14-days approx (
for Bitcoin).
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.