Legal Question in Business Law in Washington

It depends quite a bit on how the deal was structured and what the contracts say. Also, it sounds like an amusing case of a failure to engage in appropriate levels of due diligence on the buyers part.

What does the purchase and sale agreement say about the included obligations and cutoff date? What's the form of the business entity? Were there any personal guarantees on the debts?

With answers to those questions the answer to yours may (or may not) be found.