Solution, be honest: "Masks work, but we don't have enough and need them for hospitals so you're not allowed to buy any. Wrap a tshirt around your face instead, it's probably better than nothing."
Huh come to think of it, banning the sale of masks would have been the most brilliant strategy to get people wearing masks.
Imagine if instead of putting out a press release, they had quietly banned selling masks by retailers and then 3 days later when people caught wind of it explained the shortage mean they were only for hospital workers.
All the anti government reactionaries that are now anti-maskers would be the most ardent mask wearers.