I was on the ground at YWOL yesterday and monitored the radio exchanges in relation to this event.
There were a number of aircraft operating around the circuit area and near the coast, and as far as we were able to determine not one of them squawked 7700. I heard the Rex aircraft communications, plus some of the local aircraft from the flight training school, and they soon verified none of the training-school machines flying were mis-tuned as far as codes went.
We checked the transponder of one aircraft that was suspected of being the cause after it taxied back to the hangar and before the pilot shut it down and found the transponder hadn't been switched on...when we powered it up it came on with 1200 (it was a Becker transponder). Although he should have been using the transponder, his failure to do so on this occasion it clears him of any further suspicion.
A couple of aircraft near the coast conducted visual searches to see if an aircraft had come down in the water off the beaches around the area in question, but nothing was sighted. The pilots were not SAR-trained, so their search was of necessity cursory, although we were open to the possibility the emergency might be genuine and someone had gone down. However, this did not appear to be the case.
So, for those of us at YWOL yesterday, the cause remains unresolved, and we are no closer to determining whether the event was triggered by a local aircraft, or by someone cruising down the coast with their head in the office who inadvertantly hit the emergency code on a transponder or had a touch of finger-trouble.
Rather mystifying...and I for one hate mysteries.