Heh, but it still doesn't make sense from the way Nolan's Batman worked. He never brought down small-time crooks, he went out for the big organized mob style crooks. By the time TDK was over, the mob was completely crippled by The Joker, Batman had captured The Joker, and of course, killed Two-Face. Plus, like it's been stated so many times now, he was completely injured, so he couldn't have worked. Even if the Dent Act wasn't in place yet, he still had nobody to go after.
And if he was out and about, I think it would have been 100x easier to spot Batman hobbling around with a cane.