You'd think the plane would be equipped with a switch that triggers a signal in the event of ejection.
Our chutes were equipped with locator beacons, set off when the rip cord was pulled.
The aircraft was equipped with the ACES II ejection seat, and assuming the pilot set the switch on the seat correctly (and we set this religiously - I'm an old F-15 pilot), the beacon transmits when ejection is initiated. Pulling the D-ring (rip cord) is a contingency, as the parachute opens automatically based on aircraft parameters (speed, altitude, etc.).
The chute sighting is indeed good news, as it at least indicates an ejection.
