Simon had thought of going out the usual exit, but he opted for another route, especially after seeing Mal and Zoe talking. He didn't need a confrontation, not after what just happened. Instead, he finished his rounds and left the building/complex another way.
The good doctor didn't have any set direction, though perhaps his steps were slightly Police Station bound. Yet, he wasn't going to make it anytime soon. His mind was working on how to handle women; it wasn't easy. He didn't know how Mal did it, and any relationship he had with the women on board Serenity hadn't helped him to understand any better. He supposed he could have sought out Inara, but he had a feeling that was the worst place to go. Kaylee would seek her for guidance and comfort; the doctor was smart enough to understand that.
As he mulled over his next step, literally and figuratively, he paused in front of a Fringe hardware store; it seemed so simple, so innocent. He'd heard the term "mom and pop," and this was definitely it. Free associating led to River dancing in some sort of celebration; of course, it also led to his sister being tied to a post to be burned later, but he tried to focus on the happy moment.
Other people might have thought Simon was looking at his own reflection in the spotless glass, the owner seemed proud enough of his/her business to keep things nice, but Simon wasn't even mentally present to take in how he might have looked. For now, he was simply staring into "space."