Definitely sinister
Definitely could have been something more than a model rocket.
A Soviet-vintage SA-7 Strela handheld IR SAM has an effective altitude of around 5000 feet and would look like a model rocket (though an Israeli A-4 Skyhawk had taken a hit from one at 11,000 ft. during the Yom Kippur War if I remember right).
The SA-7 wouldn't be able to guide if not fired from behind the target though... FIM-92 Stinger has an all-aspect IR seeker and an airliner at 3K ft would be an easy hit for it.