Depends a lot on the cop and the beat. If it's an area that is experiencing a lot of bike thefts, and the police are taking a lot of flack about "not doing anything about it" (as if they really could), then the cop probably wanted to go through the motions of checking out the photog's driver's license to appear to be responsive to the plaintiff. It's dumb, but it gets guys like that off their backs if they can make it look like they're trying. Kills the time 'til the end of their shift.