Its somehow impossible that a coin sent to your wallet address will disappear without any trace. Its either the wallet was hacked or hijacked by someone who has access to your private key to that wallet. Checking the transactions history using etherscan.io or the transactions done/carried out in your wallet will give a trace. If the wallet was not hacked or hijacked, it means that the coin is a shit coin, which is the result of scam projects filling the crypto space. Otherwise check if the website, telegram channel/group still functioning.
For me, the coins/projects that ended up being shit coins/projects was sent to my wallet and I can find them, just that their price are all blank.