It actually depends on what type of mistake was made. Basically if coins were sent to a totally non-related address then the coins are actually lost forever. Something for example like sending USDT ERC-20 coins to a USDT TRC-20 address literally means the coins are lost forever since the address is totally invalid and non-related based on the chain.
However a situation where two different coins on same network are sent to the same address mistakenly then it can be retrieved because most times the anchor address of that particular network can receive any token or coin on that network.