It's an interesting question.

>TLE is used to track whether the satellites are in orbit or not

Not exactly. TLEs are used to predict positions of satellites. The TLE or [Two line element][1] is carefully constructed so that a propagator (usually [SGP4][2]) can predict positions based on the values contained in the TLE.

TLEs for the earliest spacecraft may have been generated much later (see answers to [What was the first proper Two Line Element to be generated?][3]) and they can be generated with epochs (the T=0 datetime inside the TLE where it may be most accurate) in the future as well. (see answers to [Can the TLE epoch be listed as in the future? How?][4] and also [Is SGP4 propagation necessarily more accurate near the epoch chosen for TLE generation?][5])

But as the public, we don't really know when the actual *measurements* of the position and/or speed of the satellites are made, or the "secret sauce" used to cook those measurements into a TLE.

So really no, the TLE doesn't tell us much at all about the condition or even existence of a satellite. Usually if they keep generating them, the spacecraft is probably there. But it's not a reliable verification of the spacecraft's existence or condition.

[1]: https://en.wikipedia.org/wiki/Two-line_element_set
[2]: https://en.wikipedia.org/wiki/Simplified_perturbations_models
[3]: https://space.stackexchange.com/q/19887/12102
[4]: https://space.stackexchange.com/q/28365/12102
[5]: https://space.stackexchange.com/q/29751/12102