How Many Bitcoins Are Missing?
One cannot distinguish between saved and lost coins, because it is only possible to prove ownership of a private key, but impossible to prove that a private key is lost. I.e. nobody can tell the difference between whether I just haven't moved my coins for five years or I lost the key.

Coins cannot be counterfeited. 

Coins can only be spend by having access to the private key. Rediscovering a private key, though, is extremely unlikely and due to the amount of computation required most likely not profitable.