Is there something wrong with my dobro?

I got a Gibson Hound Dog Deluxe off of E-Bay. It sounds great as an
acoustic but there is something wrong with the pickup. At first no
sound came out of the amplifier - not even feedback.

Later it seemed as if the pickup was working but only when the guitar
was in horizontal, "slide" position. When I held it vertically in
"fretting" position no sound would come from the amplifier... I
rotated the guitar slowly back and forth like a circus clown to verify
this and then I concluded that there was a loose wire, so I removed
the tailpiece, and found this:

http://zigfried.net/dobro_wire.jpg

It isn't simply a loose wire - it's a wire that isn't attached to
anything. I finally had to disassemble the dobro and inside I found
that the piezo mechanism was bolted to the spider bridge, with one
black wire connecting to the tailpiece plug, andtThe yellow wire that
doesn't connect to anything also connecting to the tailpiece plug.

Every website that sells this model states that it comes with a
Fishman resonator pickup. I looked for an online schematic but none
of them made any sense. All of the schematics that I found show the
single black wire leading from the piezo mechanism to the tailpiece
plug but no additional wire that doesn't connect to anything.

I have also read documentation and message boards recommending a
Pre-Amp - however I have used sound-hole and piezo pickups with
acoustic guitars and other instruments that did not require a pre-amp.
Also why was there a sound initially when the guitar was in "slide"
position? It seems like this is only a recommendation to improve the
sound quality, and not a requirement.

I would definitely appreciate any help.