I have had my bike blow under me one time in the rain as well. Normally I dont mind riding in the rain, and I dont mind riding in the wind. This night it was dry, and a huge storm was blowing up. As I was heading home it was the kind of wind that picks stuff up in the fields and slings it into you, and then it just started a downpour. The roads were slicked up from road scum, and a huge gust just blew the bike under me, like you were describing. It lost traction and went sideways. I pulled off and hid under a banks porch. LOL
I know that there are things called micro bursts. They crash airplanes, break trees, and blow roofs off houses, where around them the wind is 30-40mph they can be 60-100 mph winds, they blow down, hit the ground and spread out. You may of rode into one of them.
It was a combination of freshly wet roads, stronger than normal winds, and crappy tires that came stock on my ninja. Relaxing and letting the bike do what it wants recovers it if it can be recovered. I dont know who said it, but when it gets real bad, let the bike have its head, if it can recover it will. Dont believe it? Jump off the bike and watch it ride away with out you. LOL