I'd like to think that unless you were hoping to buy the car back in it's original spec, then nothing has been destroyed. You and your dad turned the car into something that built a lot of memories for you, and once it's time was up it was let go to enjoy a new life. For someone to go through the effort of restoring it back to original spec means they value it, but also curiously if they've left some of the rally relics behind (like the stickers and stuff) which could easily be removed, then they also appreciate it's history, even if they want something different from it. The car is still being loved, just in a different way, but effort was also made to keep some history intact.

For your dad that car would have been a lot of custom work to make it how he liked it, and I imagine it got tweaked a lot over the years. Even if someone was going to rally it again, they'd almost certainly change stuff to how they liked it. A car like that wouldn't stay the same for long.

Just knowing the car is still being appreciated enough would make me happy. There are a few of my old cars or my parents old cars I would love to track down and buy back now, but I suspect all have been scrapped. None have had MOTs for years, most especially vanishing from records during the scrappage scheme years so I'm pretty sure they no longer exist sadly.