a blood dragon appeared attacked some bandits then decided he wanted to fly straight up through the sky and dissapear. has this happen to you?

Ummmm no haha.

it was a good laugh, but i get very few ramdom encounters so i was hoping for a battle.

I've had this happen several times, but only after using Dragonrend on them.

Nope, no disapearing dragons... But while fighting a dragonfrom horseback my horse suddenly decided to learn to fly.

He was probably trying to investigate the http://www.uesp.net/wiki/Lore:The_Lunar_Lorkhan theory.