Well you posted this in the "Economics" section, so let's make this about economics.
People have an amount of BTC. The higher the value of their BTC, the more likely they are to keep it in safe locations or spread it between different places. So the chance of them losing their BTC decreases exponentially as the price rises.
If they lose BTC, the supply decreases, therefore making the remaining BTC supply (marginally) more valuable and making people less likely to lose it. So it never reaches a point at which there's not enough left.
So basically, no. It's impossible.
They lose that bitcoin but it is not gone. It cant just disappear from wallet. The fact that the person cant acces the wallet doesnt mean the bitcoins doesn't exist. Yeah, bitcoin price is partially determined by the total supply but if you lost your bitcoins wallet thats not going to decrease the total supply. It will remain the same. The price grows every day because it is harder and harder to mine it not because bitcoins are lost every day
There is no practical difference between a coin "disappearing" and a coin being unable to be accessed to be spent. From the perspective of supply and demand, an inaccessible coin is indistinguishable from a non-existent coin in that neither will factor into supply. If a coin were to disappear, or simply become inaccessible due to lost private keys, it will decrease the supply available, and decreased supply leads to a higher price as stable demand chasing fewer coins necessitates a higher price (theoretically). Supply isn't the number of coins that are mined, it's the number of coins that are accessible.
Having this one said, based on OP's point. no it will not lose it's value it will even result to a higher market price since the supply that is circulating will be less and when higher demands occur it will result to higher price per piece of coin.