Legal Question in Criminal Law in Massachusetts

I don't have a ready answer to help you resolve this situation, whether that involves sending them money or trying to return the shorts. That notwithstanding, as long as you have the shorts in your possession and you haven't paid for them, it's theft. That shouldn't be difficult to understand, and the fact that several days have passed doesn't make this any better for you. My suggestion is that you contact a criminal defense attorney, and have them negotiate a return or a payment. The sooner you get on this, the better it will reflect on you. If the store can identify you and you wait for the police to come calling, you will have a bigger problem than you have now.