Im trying to learn as much as I can about bitcoin, but there is on thing that has been puzzling me. If the number of bitcoins is set at X number of bit coins, then what happens when bitcoins disappear from the pool. For example if I have a thumb drive with 1000 bit coins in its wallet and I drop it in the ocean and there is no back up, are those coins lost? People lose stuff all the time so would the number of total bitcoins remain the same if  some coins are out of the loop for x number of years? As an example I bring the recent story on the news of a man who lost a hard drive with 7500 bitcoin.