As a business there are a lot of financial records to manage Is your small business making a profit? Have you been filing IRS annual income taxes to include your business? If not, they I'd say you don't have business in flying. On the other...
You should have detailed close-up photographs of the drone before you sold it. There is no history of cracks just happening.
You'll probable just have to work out a deal with the buyer and follow eBay policy.