Agree with Centaurus,
Back Seat Driver, there would be additional indicators of active fire or a genuine activation, other sensors going off, systems showing signs of degradation due to fire, try reset the detector, etc the list goes on, the FL the aircraft was at also would be just one clue.
red_dirt, presuming we are talking about the B738, can you tell me how to reset the wheel well fire detector?
Can you tell me what other sensors there are in the wheel well for fire detection?
Can you tell me if the wheel well fire warning ceases, does that mean the fire condition has ceased as well?