This story is so upsetting to me. I empathize with you mazal77 – you are in the right 100%.
Regarding being oveir any issur, I’m sure that since we hold of Dina Dimalchusa Dina, the store owner is certainly wrong on that account.
If you could (or should) report the owner to the Dept. of Consumer Affairs is proof that he did something against the law. There are many sources in Chazal which discuss misleading a potential buyer.
I hope that you told the owner or manager that “he lost a customer, with a whole family of eye glass wearers.”