the EXACT same red barrette ?
The girl jogging with the guy, then she stops, for two or three seconds you see clearly the barrette, then she runs off and you see the killer's car following her.
The red barrette Denzel sends to the detective (and which we know he bought) is exactly the same model.
Like cars or shoes, there are hundreds of models of barrettes, different shapes, sizes, models, shades of color.
From the information we are given in the movie neither the detective nor Denzel have a photo of the exact model of barrette so how could Denzel know the exact model she was wearing and buy the same?
The fact that the two are exactly the same is it simply a slip up / mistake from the director forgetting there are hundred of different models of barrettes, or is it may be on purpose to imply something?