A trick I never heard of until your post.
In the 1970s I heard restrooms had lots of “Out of Order” signs to prevent drug addicts from shooting up and people from having sex in them. All, or nearly all, were still working fine.
Then “No Vacancy” on thousands of motels off interstates. But if you ask, and you look respectable, they said “oh, we have a vacancy after all.”
Another was a Korean nail salon located in the outer area inside a large supermarket-discount store which had one less than the illegal amount of marijuana plants under lights. (When that was illegal). Exactly one. So could pretend for assumed personal use misdemeanor.
EXACTLY - and each one that I went to actually did have bathrooms, but funny, they seemed to be ‘out of order’.