If it really was a MANPAD, it might have been a old Soviet Strela. They have a nasty habit of going anywhere *but* in the direction of the target - assuimg it doesn't detonate on launch or at some random point in flight (usually close to the launcher, ruining the operator's day). There are literally millions of Strelas running around the world arms markets. They're more dangerous to the operator than to an aircraft, but they're cheap and the operator might get lucky. Me, I'd stick to throwing rocks at a landing or launching plane, it's more reliable and more effective. :-P
Of course, what they probably saw in all reality was some kid setting off a big firework or something equally stupid and innocuous.
Some have called the old SA-7 MANPAD system a Redeye missile with Soviet-level quality control. It was cheap to make but its accuracy left much to be desired if the IR sensor wasn't kept in working condition (which was way too true in the hands of terrorists).