If you've set up automatic backups before and would like to recover your receipts, try the following:

  1. Open the menu button (3 dots in the top right) and selecting the "Backups" menu
  2. Tap on the "Tap to Configure" option and select Google Drive
  3. Normally your past backups will show up right away but sometimes you have to close the app (swipe from recents) and then relaunch for them to appear
  4. Tap on the backup that you wish to restore

If you need some more information, this guide walks through the process in more detail: