If the amount of the Bitcoin that people holds begins to be lost because they have no control over it in the Blockchain forever, due to the lose of their private keys, the effect will be deflation.
Deflation is simply drop in market value as against inflation, bitcoin cannot go under deflationary trend all because of the lost coins to the blockchain technology, what you should know concerning these is that, every lost coins will be sent back to the network and not as if they were there somewhere hanging in wait of someone to claim them, indirectly, they have been redistributed back to the network and which is part of what we see influencing the market price and the demand and supply of what the bitcoin price gives through its volatility.
Although the amount of Bitcoin lost through this means might be insignificant compared to the amount that is in circulation now, but if the loses keeps occurring in the future, it will certainly lead to deflation
Just to add more on this for further clarification, i don't think its common for you to see someone making a huge amount of bitcoin transaction to afford making a silly mistake, i don't think the whales can afford to do this, maybe common to the little holders or newbies and these little amount were being returned back to the network in circulation to everyone holding.