From a younger couple a couple of years ago:

They were tenting in an isolated lakeshore location. He got her talked into a little romantic interlude on a blanket in the open air. As she got...seriously involved in the situation...the whim struck him to say "someone's coming". She, quite unterstandably, mistook his meaning. A very short time later, he was alone on the blanket and she was inside the tent.

I know it's "hearsay", but, from watching her while he told it, I would be willing to bet that it's a true story.