Everything I've read about non-business bad debts relates to personal loans that have been defaulted on, I currently have 2 clients taking losses for personal loans that people filed bankruptcy and the courts told them theyre getting nothing from them, so we took the capital loss and Ive never had a reason to dig any further. 

If the regs state that deposits on purchases that go unfulfilled qualify as a non business bad debt then you may have some capital loss to utilize, be sure he documents the efforts made to get the deposit refunded.