Impossible to recover or recoup or overcome(adjective)
WordNet. Princeton University. 2010.
Use "unretrievable" in a sentence
"Then the other computer to which that socket was open refuses new socket connections because it still has an open socket to my "unretrievable" client socket."
"The $200 in earnings that hadn't been paid out yet are unretrievable, and she can't open a new one."
"It takes a lot of hard work, involving deliberate action from a team of seasoned professionals, to make the evidence unretrievable."