I'm assuming you got something through Paypal or an invoice directly from him. That would be your receipt. While i have never dealt with Bob Clark, like Deborah calm said, he is busy and he is a larger scale breeder so you probably wont get quick personal responses. This is why i personally try and deal with small time breeders who do it for the fun of breeding and not to make cash. I have always been answered within 6 hours from them and usually end up having conversations with them about other snakes etc. A couple guys who are awesome to talk to are Chris Wolf and Matt Cook. Those 2 would be my go to breeders for locality and obscure locality BCC and anything kahl albino like sunglows, corals, snows and moonglows respectively.
I personally wouldnt worry. I doubt Bob Clark would try and stiff you.