I actually meant to present that as: Because I didn't flip the switch.

A counterfactual requires posing a situation with changed facts. I stand by my statement, saying "X because not Y" is not a counterfactual on its own. "not Y" is still a (potentially) factual statement. And guesses still aren't counterfactuals. "Maybe the lights aren't on because we didn't flip the switch?" That's a hypothesis, and a testable one. Still not a counterfactual. If we know the flip hasn't been switched, then it's just a fact even if the statement is in the form of not X.