You got lucky! I check my mirrors when I change lanes, and then I turn my head to double check. When I change multiple lanes, even if I don't see any cars in my mirror, I still turn my head when I change each lane because there might be someone speeding faster than I am, and they can sneak up on you quick.
You were in the far left lane and only looked over your shoulder once to change 3 lanes? You are partly responsible for the surprise, sorry.
