You can add in your forgotten drives via the menu of your app!
Navigate to the menu of your app and click the “Add a trip manually” button to add in the details from your trip.
Using an Android phone? That button will instead say "Forgot to record a trip?"
UPDATE 5/20/20: For Android users unable to add their past mileage
If you update your app via the Play Store, the latest version contains a fix that should allow you to effectively add past mileage!
Thank you in advance for your patience.
-Stride Member Experience