If you're talking about IMAGE it was known where it was NASA just didn't know that it was still transmitting. IIRC the discoverer actually used the orbital elements to determine what satellite he was seeing. They still had an active and accurate TLE for it they'd just stopped checking because NASA thought it was dead in space after the eclipse a couple years ago failed to reset the broken power supply. [0]

[0] https://skyriddles.wordpress.com/2018/01/21/nasas-long-dead-...

"the thing about the dods tracking capabilities" is true. They know what's up there, down to lost tool bags.

The instances you're thinking of are either "lost" as in "presumed dead" (like IMAGE) or non-Earth orbit probes (like ISEE-3). IMAGE was never untracked, and ISEE-3 was never supposed to be tracked (but its location was still known.)

If the dod tracking is really fantastic, the smart move might be to not demonstrate it remotely publicly.

Remember when the NRO gave NASA two space telescopes no one knew they even had, bother where comparable in scope/complexity to Hubble.