Could it be that after say 100 years a lost coin is returned to something like a mining pool? Is there any other way to return or re-mint lost bitcoins?
Yes, with the
Dead Man's Switch You can program in several layers of transfer. After 30 days, the money could go to your close family. After a year, it could go to some website you sign up for that will specialize in determining your identity in more conventional ways and give the money back to you or your next of kin. Or you could make it go to some favorite charity. You could also have it go to a miner, but I'm not sure what the point is. I guess if a lot of people did this it would bring bitcoin transaction fees down.
One last thing to remember is that when the money finally disappears, it makes every other bitcoin user a bit richer, exactly the opposite of inflation. So in a sense, even then it's not completely lost to the world.