Hi, welcome to the board.

This topic has been heavily discussed already throughout the forum. Loosing bitcoins is not an issue as they are highly fungible. Today they can be divided up to 8 decimal places ( 0.00000001 BTC = 1 satoshi ). If the need arises in the future, we can modify the protocol to allow for even more decimal places.

Once you understand this concept, you realize that the number of bitcoins in circulation doesn't really matter and is only a matter of convention:

21 000 000 BTC
21 000 000 000 mBTC
21 000 000 000 000 uBTC
2 100 000 000 000 000 satoshis

And hypothetically, if we increase the number of decimal places to 16 in the future, we would have:

210 000 000 000 000 000 000 000 units

So even if all the bitcoins except 1 are lost, you can still run a world economy on it as long as it is fungible enough ( you set enough decimal places in the protocol ).