If the company the OP gave money to for a pre-purchase actually did declare bankruptcy and go thru court already then the OP, investors, suppiers and such lost out unless the companies assests were distributed to them. If a bankruptcy did not happen then the company still owes refunds or parts. If it did then technically John owes him nothing but ethically and for his reputation still does.
An entity such as a corperation or an LLC does not have to file bankrupcy to dissolve. Many small business entities are just abandoned and left with no assets and no activity. If the creditors believe that there are assets to be distributed, then they must petition the bankrupcy court to force the company into receivership, take control and distribute the assets accoding to law. I'm not making any judgement here, just pointing out that a bankrupcy proceedure may not have happened. The old company may still remain as an empty shell, or may have been disolved. Not the same for a sole proprietorship - in that case bankrupcy is the only way to escape debts without paying them or receiving a voluntary forgivness by the creditors. Another thing is that an LLC or a corperation is a separate legal entity from its owners and shareholders. The companys debts are not the owners debts. But if the company fails and owner begins voluntarily paying the companies debts out of his own pocket, he may be then be found responsible to pay ALL the companys debts. I would think that JP is aware of this and would be concerned that personally paying $300 of the old companies debt could make him personally responsible for perhaps mountains of bills to vendors, landlord, IRS, etc. Again, I am neither judging or defending and have no first hand knowledge. I'm just speculating.
Edit: after reading the above 2 posts, which happened while I was typing, I'll add the following question: Didn't US Car Tool start in a different state, like NJ or NY, then move to NC? If so, perhaps there is where you will find the business registration for the old company.
