[Terriergal]

Is there some kind of jamming device they could have used on the missiles?

[Cold Heat]

Flares are the best counter-measure for a thermal targeting device. There are some other methods.

According to the article on this missile, it is prone to confusion regarding the radiant heat from the ground. The plane was taking off. The launcher has no radar to trigger any kind of protection, and the time element was too short for the planes radar to pick up a missile and deploy any counter-measures.IMHO.