After going back, what I was thinking of was that @AmusementLeaks posted them on Twitter and they were linked and analyzed on the here. There were foundation and other plans that were posted which were complete scans of the page including title block. We learned quite about about place from details in there.
The Twitter and the resulting imgur for reference are here:
Amusement Leaks (@AmusementLeaks) | Twitter
The earliest reference on the site I could find was here:
Wizarding World - Diagon Alley Discussion - Part 2 | Page 73 | Inside Universal Forums
Those essentially are blueprints, but I see the distinction between posted on the site and linked to posts elsewhere, even if the source material ends up posted directly on the site.