I would've most likely done #14, too, although it's hard to imagine how the boom sounded so I think #11 could be possible, especially if I immediately remembered that the President was in town. Or let's call it #11 but without leaving. But the fact that nothing shook and you didn't feel any concussive force or hear anything else usually indicates that you aren't particularly close to any explosion and not in any immediate danger.

Actually, one could theoretically argue that leaving may not be the best choice, too, since you apparently didn't know where the sound was coming from so you could have potentially travelled into some situation. At least you were safe and unaffected right where you were.