As far as I know Mayer didn't work on Leave it to Binky past the first two issues, and I'm not sure how much he did in those. The story in issue #15 is actually a Scribbly story from when the title went on hiatus for about a year. It's not quite as simple as "the stories in Binky 15 and Buzzy 32, 33, 34 and 39 were intended for the unpublished Scribbly #14", though. The Binky 15 and Buzzy 32 came out the same cover dates as Scribbly #12, and the Buzzy #39 is actually cover-dated 9/10 compared to the Scribbly #14's 10/11- BUT the story in #39 actually clearly follows the stories in the #14; that ties into the page count drop from 52 to 36 around then. Meanwhile, while I think the stories in Scribbly 12 & 13 and the batch of strays could accurately be called the material intended for Scribbly 12, 13, & 14; saying that the strays were intended for Scribbly 14 is not correct, I think. (There's some other stray material in a couple issues of Sugar & Spike for that matter; a Little Snoony story and a Cartooning page.)
All of which is probably something very few people even care about, but I love trying to guess what was going on from the contents of the books. It would help if I had more than half of the relevant issues.
I'm lucky enough to have all 3 of Mayer's major first issues: Scribbly, Sugar & Spike, & Three Mousketeers. The 3M's aren't bad, but not nearly as good as S&S or Scribbly. I've only got a couple issues, plus most of the early 70's reprints.