I rarely ever get anything but dust and water spots in the air, and this one really has me stumped, I'd say dust or bug if it didn't seem to span across a 14' room in 1/8th a second. if the consistency of it was even from end to end I'd say dust particle, and it was in a dark room with exception of the flash.. I usually go with my first guess, any experienced investigators, again I'm not an orb person.

I think it's a hair or thread. Based on the shape, it makes the most sense. It's just VERY close to the lens.