Open WhatsApp
Check the chat list for the conversation
Use Search to find the contact or group name
Scroll up in the chat to view older messages
Restore from a recent backup if the chat was deleted
Reinstall WhatsApp and verify your phone number to trigger backup restore
Check Google Drive backup on Android
Check iCloud backup on iPhone
Make sure the backup was created before the chat was lost
Ask the other person to resend the chat if no backup exists