Actually, depending on the type of loan, it could be that the business owes the 15K, not the business owner but I guess that would depend on whether the business was an LLC or a corporation.
If the debt was a business debt, the debt went with the company. If this is the case, they're going after the wrong people.
If in fact the business was registered as collateral on a loan, the new owner would have been aware of this debt when he purchased the business.
From the sounds of it however the first lawyer was correct: he's SOL (shit outta luck).
BTW: you may not be able to stop the sale of the house but if this was a personal loan, you can still get a judgement filed against the borrower and if you keep track of him, (it WILL be up to you) once this judgement is filed if he returns to Canada and tries to get a credit card, loan, whatever, it will be on his record.
I'm not sure what the limit now is for small claims court but you don't need a lawyer for it (especially if you have signed contract and records of payment/non payment).
So, this guy's leaving the country, has he divested himself of all bank accounts, credit cards, property, cars etc here?
If he has anything in Canada, you can attach a lien to it.
(btw, dream has the simple straightforward approach to debt collection).