Happens to me a couple of times, not just with mantises, but with grasshoppers as well. One time, a cricket as well. I like to hold bugs and look at them as they crawl on my hand, sometimes they just... see my face and go for it!
What is also common is sometimes I get so close that they can reach my nose and they crawl onto my nose.
Even funnier, one time I had a mantis get startled by the movement in my eye. It briefly threw a threat display.