I understand that parts listed for sale are for sale until money is exchanged.
If someone asks for a quote and some one else shows up at the front door with cash in hand. The first person to exchange money gets the part.
A request for a shipping quote is not an agreement to purchase. Providing the money is an agreement to purchase.
If the guy that inquired about the shipping quote is suddenly also dealing with an unforeseen emergency, then he should deal with the emergency. After the emergency is resolved then he can resume his shopping.