Retrieve / Restore Deleted Messages or Contacts in Gmail

If you’ve deleted a message permanently by clicking Delete forever in your Spam or Trash, it isn’t possible to recover the message.

If you’ve moved a message to Trash by clicking Delete, but it’s been fewer than 30 days and you haven’t permanently deleted it, follow these steps to put it back in your inbox:

• Sign in to Gmail.
• Click Trash along the left side of any Gmail page. (If you don’t see Trash along the left side of your Gmail page, go to the Labels tab in Settings, then click the show link next to the Trash label.)
• Locate the message you’d like to move to your inbox, and check the box next to the sender’s name.
• Click Move to Inbox. [source]