Actual physical or electrical damage is really the only way to brick the Z; since you weren't the one who broke it then what happened is anybody's guess - a fall, water ingress, voltage spike etc.
If the seller represented it as a working unit then you should be able to claim back your money...
(oh, and as for last resorts, you *can* jtag the Z, but it requires opening the unit up and soldering to the signals directly - the missing components just remove the ability to use the connector to do it non-invasively.)