Evidence and information is going to be gleaned from the explosive device, for certain. Stuff the planter of it will never have even thought about, let alone taken precautions against.
It was an improvised device - so not a product of a very structured, experienced group of terrorists with money and years of planning behind them. That doesn't make it any less dangerous and horrific for the people who were the targets ( or just passing by), but it will make him/her/them easier to find.
It strikes me that this will turn out to be a fairly local person, because it's a fairly local target. And that support for any extreme views will start dropping away in the area now - bombs have that effect on civilian populations. I would think information is starting to flow in already.
All the attention this is going to focus on the area is going to be very good for Stephanie's case, I think. All the searches, questions.......I hope in the process, some information turns up about her, and her possible location.