With all due respect to Norman Whitfield and Barrett Strong, "I heard it through the grapevine" is not much of an answer to "I bet you're wondering how I knew."
@efd I always thought that if one had to be "extra careful" about one's affair, meeting at the same place and same time was a bad way to do it, to say nothing of recording a song about it and releasing it as a single. No way Mr. Jones didn't find out.