The only thing that man has over the likely thousands of others that in some way participated in the event is his skin color. Everyone else there had those same properties. So if we are considering the population of people in the general area at the time, then no. They used only his descent. They, and djanogo[edited], used P(arabic|terrorist) to justify a search. In order to justify a search you need a reasonable P(terrorist|arabic).
Assign some reasonable numbers to each factor off the top of your head, work it out on a napkin, and come back to me with whatever figures work out to be over whatever a reasonable threshold might be.
If the bombs were really placed in backpacks that were left sitting on the ground, I would further suspect that the bomber placed them much later an hour before. Wouldn't want someone to steal your bomb...
Furthermore, maybe the sick fuck wanted to watch so he stuck around at a short distance instead of booking it.
Who knows.