Yep. That's true and a good example.

But it isn't going to be anti gravity machines. Any machinery type technology like that wouldn't just disappear.

Things could get buried or built over, but we still have cave paintings and stone age tools that are older than the time periods they're trying to line stuff up with. Which isn't to say that stuff could disappear, but to disappear to the extent that there is a blank slate is a little out there. It's not like if the planet got hit by a comet today (and it wasn't some tidal force event that ripped apart the crust, some event where life would continue, although in not great conditions) all traces of our civilization would be gone in 12,000 years. Basically everything would burn, erode, or decompose but there would still be things that would survive and get buried somewhat 'safely' and last. Like glass, maybe some metal tools wouldn't oxidize, although I think most plastics and everything else would be gone.

They can be advanced in the sense that they didnt just have no concept of society, didn't use tools, written language, build carts or levers or whatever, but it isn't like we're going to find out they were advanced in the sense of ultrasonic cutting tools. Language and context is important.

The Egyptians might have had an advanced method of understanding how pulleys and levers worked, or non conventional methods for using their resources like sand/water/copper/granite for cutting, that we haven't continued to use. Maybe they had a recipe for a unique super hard rock tool like concrete that they used to cut things, like a hardened or refined limestone or granite tool.

But that should be separated from the Sci fi tools and ideas lol.