Check your WhatsApp chat backup and restore it
Uninstall and reinstall WhatsApp
Verify the same phone number and Google Drive or iCloud account
Restore the backup when prompted during setup
Check notification history on Android if it was enabled
Use a notification log app on Android if previously installed
Ask the sender to resend the message
Check linked devices if the message is still visible there
Use local backups on Android if available
Use third-party recovery tools only if you trust them and understand the risks