I've seen aerial photos of the place, and it was a thing in the earliest ones I have access to (1947), and even seems to have survived a decade beyond Hurricane Hazel in 1954, existing into the 1960s. The place was called, I gather, "The Willows", and started off as a set of cottages, at least some of which were winterized into homes by the early 1950s.
Here's how the place looks today. That bit of open green just to the left of where the trails meet is where I brought Larry to try out his metal detector. Apparently it works... if finding old pop cans is to be the measure of success. :)
While I couldn't find any pictures of the community itself, the City of Toronto Archives does have a number of pictures of the valley with, first, the Bailey bridge being set in place at the end of the 1950s, and then the 1965 bridge (called "The Willows Bridge") under construction for contrast.
The following are views from 1965, when the modern Willows Bridge was being constructed.