BT, Rav Moshe wrote that there is no marit ayin by mistakes in halacha. People are required t learn. Marit ayin is only where a reasonable person could make a mistake regarding a fact (e.g. if somebody walks into a treif restaurant to buy a Coke). However, he was machmir on himself.
Regarding emergencies, these are obviously exceptions but someone whose wife wants him to pick up something on the way home can hear it afterwards on the voice mail.