That's not the point and you know it. Property is property. Just because it's not terribly inconvenient to replace a certain piece of property doesn't mean that others have the right to take it from you.
Bull$hit. You have the right to take your neighbor's knife from your neighbor's hand if he's threatening someone with it. Don't give me this "property is property" crap, especially when we're talking about a piece of paper that was easily replaceable with minor inconvenience.
Did he have a "right" to take it? Do you mean did we, as society, give him the legal power to keep that prescription?
Of course not.
Given his beliefs, did he think he had the moral right to retain the prescription?
Of course he did. As a matter of fact, returning it to be filled by someone else would make a mockery of his beliefs.