To complete a delivery the driver must capture a signature or a photo, so every delivery has at least one. Photos come from the live camera only, are made small on the phone and are uploaded in the background: with no signal the driver's Today screen shows "Sending … updates" and they go by themselves once the phone is back online, keeping the real delivery time. Ask the driver to open the app with mobile data on so waiting updates are sent.
If the office marked the job delivered with Mark delivered, there is only the receiver's name, no signature or photo.