A number and a time on what you sent
When you send from the app, the order is stamped with its own number, the date and the time, and a confirmation reaches your phone. When a delivery comes up short, you have the order to point to. A call or a voicemail leaves no such record.
Each app order numbered, dated and timed
Confirmed by push notification or text
Something firm to hold a short delivery against
Who sent it and when, on record