In the following sentences, should "didn’t happen" or "hadn't happened" be used?
Sales have gone down, and obviously we’d prefer it if that didn’t happen / hadn't happened.
Sales have gone down, and obviously we wish that didn’t happen / hadn't happened.
I thought "hadn't happened" is correct because the sentences are about counterfactual past scenarios. However, the Longman Dictionary uses "didn't happen" in the first sentence. Is it an error or an examlpe of language change?