Honestly, losing a bunch of knowledge as a civilization isn't even that hard to accomplish.
Lets imagine a point 200 years in the future. Everything is on the internet. There's no reason to have books, manuscripts, etc. You can already see this now. Where are your books? For us, we might own some. But for a lot of people, it's fucking Kindles. It's E-books. Its convenient, doesn't take up space, and you can take an entire library worth of books stuffed into the front pocket of your backpack.
Now, imagine that exact same thing existed 10,000 years ago. Electricity, internet, the whole works. And then - something happened. I dunno, solar storm, major flooding, whatever. A fucking cataclysm that ended things. Look around - look at how dumb the average person is. Is it really that difficult to believe that we would revert to straight stone age very quickly? What would you be doing? Could you forge a knife? Could you build anything more than simply lashed stone tools? What if you didn't even have any reference books to look at? What if you couldn't look up recipes, or how-to guides? It's not even that much of a stretch to believe that once the very few people who actually knew how to do shit died, that there wouldn't be any useful knowledge left at all. It would be entirely thots and fuckbois trying to rub sticks together to make fire and wiping their asses with their hands.
I can absolutely imagine a situation where a super advanced civilization gets the rug yanked out from under them and because they are so lazy and so complacent they lose everything, and all that's left 10,000+ years later is their masterwork vases, buried in a tomb, the prized posession of the end of a bloodline of the kings that rose out of the ashes of the previous world. We're literally teetering on the same precipice. And in 10,000 years, some motherfucker is gonna find a World of Warcraft Burning Crusade CD ROM and wonder how we could have possibly had this technology.