If you don't know it's a Hydrangea paniculata cultivar. Look at some retail outlets or display gardens to see if they have the same one. Since this probably isn't a situation where you can cut a specimen take a good close picture, so you have something to go by besides memory.

Hard to tell from a distance. It's definitely a paniculata but which variety is the million dollar question. if you can go back and take a closer picture of the bloom it might help us.

Going off your memory, does this help at all?

http://www.hydrangeasplus.com/category-s/111.htm

Were the blooms light green before turning white? Is it showing any pink? Then could be Limelight, though it’s blooms at maturity are usually fuller. My Limelight had tons of bees on it before cooler air moved in over this past weekend.

debra