Nahhh. Lawmakers don't make law dealing with every tiny little thing that can happen to people.
If you bought something, and didn't pay for it because the vendor forgot to bill you, then you still owe him the money. In fact, you're ALWAYS going to owe him the money. Debts don't expire.
However, if you already paid, that's a different scenerio. You didn't say, by the way. But, I have a hunch you didn't pay. If I borrowed $20 from you, when does that debt expire? If I bought something from you, how long can I wait to pay, before I don't have to? 6 months? A year?