This kind of thing isn't exclusive to assisted opening knives. I've had a typical slipjoint folder open up while being removed from a pocket. The tip of the blade was just a tiny bit above the blade channel in the handle. Just enough so that the tip caught on the material of the pocket and since the knife was small and the spring wasn't very stout, that opened the blade as the knife was withdrawn from the pocket. I ended up holding the opened knife in my hand which was something of a surprise. I used a small file to cut a bit of metal off the choil to make sure the blade set deeper into the channel when the knife is closed and that fixed the problem.
A similar thing happened to a friend of mine, but his knife was larger and the spring was stiffer. He felt the blade opening and he let go of the knife. Unfortunately that allowed the blade to snap closed on his finger and he suffered a minor cut.