If you've set up automatic backups before and would like to recover your receipts, try the following:
- Open the menu button (3 dots in the top right) and selecting the "Backups" menu
- Tap on the "Tap to Configure" option and select Google Drive
- 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
- Tap on the backup that you wish to restore
If you need some more information, this guide walks through the process in more detail: