Coins don’t get lost, they always remain on the blockchain. However the keys that provide the rights to transact the coins can be lost. When a user loses access to the wallet, it basically has the effect of removing money out of circulation. The BCNA coins remain dormant forever because there is no way for anybody to find the private key(s) that would allow them to be spent again.
Therefore it is VERY IMPORTANT to backup your keys accordingly and we highly recommended to read the wallet guide that describes best practices.