A Maintenance Controller described the events that contributed to his deferring a fuselage fairing panel on a B737-300 aircraft; that was found missing upon arrival. A Contract Mechanic had incorrectly identified the missing panel location; allowing for the deferral whereas the actual panel was a blowout type and not deferrable.

Narrative

Aircraft was reported as having a missing panel on the lower fuselage upon arrival. Contract Maintenance was called to evaluate. Operations was to take pictures; send via e-mail to the appropriate desk in Maintenance Control. This all happened at turnover time. I picked up on the desk and received a call from our Contract Mechanic and asked if the door could possibly be the ground air conditioning service door. I described the door; and told him to have the flight crew show him the illustration for configuration deviation list (CDL); from their performance computer; so as to clarify that it is indeed this door. (These doors are often left open; and incur damage to the latches and hinges.) He called back and confirmed that; this was the door that was missing. I asked him also to verify that; there wasn't any damage to the surrounding structure; and he confirmed that there wasn't. We deferred the missing door per the above CDL reference and dispatched the aircraft. Upon arrival; Maintenance informed us the door that was missing; was actually a blow-out panel on the right side lower fuselage fairing. The aircraft was taken out of service and a new fairing panel was replaced. Maintenance also inspected the ducting and ran air inlet plenum for any irregularities. Our pictures from operations arrived in our inbox at departure; but the e-mail was not opened until Maintenance called; because we thought that we had determined the correct missing panel.