I think about this sometimes too but keep in mind that each BTC is equal to 100 million sats. So there's actually 2,100,000,000,000,000 sats in total. That's 2.1 quadrillion.
So the way I see it, even if over half of the supply is lost and the population of the world doubles there still should be enough for a functioning economy.
Still, I believe that not knowing how many satoshi units are really available for sale it will undermine price discovery.
The problem will just get bigger overtime.
But I also believe that somebody will eventually implement Demurrage into Bitcoin
There was no way to know how much gold or silver there was above ground or in circulation for a very long time while those were money, there's no way to know how many dollars there are, no monetary medium has ever had anything even kind of close to the certainty that bitcoin brings in this regard, and yet price discovery has carried on throughout the whole time. Bitcoin may not be perfect in this, but it's an incalculably gigantic improvement over anything else we've ever seen, so if this presents an issue with price discovery, and that's a big if, then this will also improve dramatically. This is a point in favor of Bitcoin, not against it.