Explain This

I ordered some stuff from eBags.  Some of it shipped by UPS Ground, and some of it shipped by FedEx Ground.

The UPS Ground item appeared at my door today in a great big box.  

The FedEx Ground items were not delivered -- I instead got a door tag and a request for signature.

The undelivered FedEx Ground items were smaller and cheaper than the UPS Ground item left waiting at my door.

WTF?