Haha HN, how did this post get downvotes? The second I read about "a switch needing two wires" I thought "Unless it's grounded." Interesting story, but hardly "magic"
For a switch to work a circuit must be present. Either a neutral line or a ground it is the only way to send information.
If a functioning switch has only a single wire feeding into it then it must be reaching ground through other means.
False dichotomy. You omitted a third option: magic.