What Causes Sudden Black Out,blurred Vision And Loss Of Hearing And Speech?

In a crowded waiting room at a funeral service last evening, when I first stood up after being seated for a few minutes, I felt a little unsteady on my feet. Having a history of strokes and or orthostatic blood pressure drops on rising, I felt secure in standing still for a few seconds with reliance on my cane and a hand on a Brothers shoulder. I was talking-- then with no symptoms-blacking out- vision blurring-not hearing the voices seemed to lose vocal power then become louder. At first, I thought I was still standing, then realized that those speaking to me were addressing me on the floor when my eyes focused I could see the faces very close to me and understood what they were saying, They asked what day it was? I responded properly and asked to get up but no one explained what had occurred. This is the first and hopefully only such incident (In front of hundreds of friend and acquaintances) but I have no explanation. When vitals were checked about 30 - 45 minutes when we returned home blood sugar was 101 and BP was 121/80 w/60Pulse.