That cannot be recovered; irretrievably lost. Also (of coal, oil, etc.): that cannot be extracted.

Unrecoverable.

That cannot be recovered or regained.

That cannot be regained; irrecoverable.

That cannot be recovered or got back: chiefly in reference to things lost.

That cannot be retrieved; irrecoverable; irreparable.

That cannot be retrieved; that makes retrieval impossible; irrevocable, irreversible.

Sunk without trace; usually figurative, done for, lost from sight. Hence occasionally (with partial translation) sunk spurlos. Cf. to sink without…