To give perspective on the tropical fish shopping. If RL is an aquarium owner, he likely has a relationship with a local fish store (LFS.) I have kept freshwater and saltwater tanks at various times in my life and it is imperative to have a good supplier that you can depend on for quality fish stock. Some stores have better reputations than others and, if you keep fish, you know that one sick fish can easily contaminate your tank. Even in a larger city like where I live, there are only about 3-4 LFS to choose from. In a smaller area, I can see where you might have to drive to another town to get your fish and/or supplies unless you are into ordering online. So, if he is an aquarium keeper and that was his alibi for one of the days I can bet that it was easy to verify because if he frequented the LFS they likely recognized him as a regular customer. Just my opinion and perspective.
The LFS possibly also has security cameras. Someone posted a link to a website for an LFS in Lafayette -- think it was on the previous thread. If the link was for 'the' shop then it looked like a serious LFS, and therefore likely to have security cameras.