Welcome to Qatar.
Why? There are lots of answers we can give you but none will satisfy you. But what you did is right, pretending to call somebody, but if it was me, I will take the picture of his car including his plate no. as well since you are already holding your mobile. Actually, you can make complain against them (some might say, waste of time)well, than doin nothing at all.
This are the abusive guys of Qatar who thinks that they are above the rest of nationalities simply because this is their country. The sad thing is, they are giving ISLAM a bad impression.

Peace! Have a nice weekend.