maybe it will lock on to something along the way

Assuming that this is like a Stinger, I'm pretty sure that it did have a lock on something. That's that high-pitched sound you hear shortly before the operator fires

it plays when its infrared sensor sees something bright, something hot:

Stinger lock-on tone recording:

https://www.youtube.com/watch?v=9KSJVM9Ymck

Now, it does look like it wound up heading after something other than what the operator intended, but I believe that he had something hot in its sights at the time that he squeezed the trigger.