It happened to me once
Mike, while it was not as straighforward as the scenario you described, a woman I did not know tickled me once. When I was a college student I was outside the campus student center one afternoon. As it was a long time ago, I don't recall all the details but two female students were strolling towards me and I know I had never noticed them before (and I never ran into them again). One was doing something silly - I forget what - catching my eye, and my attention embarrassed her a little. As they passed behind me to enter the building, the other woman delivered a perfect index finger tickle to my right ribs, saying of her friend, "She's not quite right in the head," or some such humorous remark.
As I recoiled from the tickle, my female stranger tickler kept moving, saying no more. So I can't say she definitely wanted to tickle me but that would be my bet.
