If a user loses their wallet private key, recovery becomes significantly more complicated. The private key is crucial for signing transactions and accessing the wallet's funds. Without the private key, the original owner has no way of proving ownership of the funds, making recovery practically impossible.
However, if the user has a backup such as a mnemonic phrase or Keystore file, recovery is feasible by importing these backups into a compatible wallet. If neither option is available, unfortunately, the funds may be permanently lost.