That's what I thought-- that it would be scanned at the shipper's post office even if she just gave it to the postman. But in looking at the USPS web site, it seems that not all their services provide TRACKING as well as confirmation. The Delivery Confirmation descriptions says

Verify delivery with Delivery Confirmation. Our low cost Delivery Confirmation service gives you the date, ZIP Code™ and the time your article was delivered. If delivery was attempted you will get the date and time of attempted delivery.

And indeed, when I returned a cell phone to Cingular at my local post office using their prepaid return mailing label with delivery confirmation, no tracking info ever showed up on the USPS site -- just delivery info. The folks at the PO said they don't scan it there. When I enter the tracking number for the missing strikes on the web site, all I get is

Status: Electronic Shipping Info Received

The U.S. Postal Service was electronically notified by the shipper or shipping partner on June 26, 2005 to expect your package for mailing. This does not indicate receipt by the USPS or the actual mailing date. Delivery status information will be provided if / when available. No further information is available for this item.