Mmm, I dunno about that. Her uncovering her dad's plan and following him in her first appearance was pretty detectivey. Not to mention the detective work she did in Robin #26 (tracking down Young El) and Robin #41 (tracking down the Ghost Dragons). Also, half of detective work in the Bat-verse is following people around, and Steph rocks at that.
And in Jon Lewis's run, she used major detective work to trick Black Canary into revealing Riddler's location, and she told Tim how she tracked down Murray.
Of course, if she's ever gotten proper TRAINING, she would have been much better.
However, Tim's so paranoid about his identity, it's probably not plausible she could have detective it outta him. I think it would have been good if he'd revealed it to her himself (Maybe asked Bats first "I'm afraid of revealing my identity to Steph because it would connect me to you." and Batman's all "Oh, go ahead. Our only connection is we were neighbors once. She's not going to figure that out.") or Steph stumbles on it accidentally, like she has to go to Brentwood for some reason, runs into Tim, recognizes him. Which would lead to Tim trying to keep her quiet as she freaks out ("Oh my God! Ro-" "OH UM HI WHO ARE YOU?") and hilarity ensues.