It is understandable that a property like a gas station might be more sensitive about random photography around and inside the plant because of the heightened potential for malicious behavior there. At least as compared to--I don't know--your local McDonald's or Taco Bell. Rigging pumps, rigging credit card readers, and arson are just a few crimes that might be facilitated by the largely unsupervised, high-traffic area and generally "seedy" atmosphere one is bound to find at a gas station.
Our MSCs are understanding when it comes to discretion and photography. There are people all over snapping random pictures with their cameras and iPhones. There is a difference between setting up a tripod and waiting for the sun to move into just the right position and pulling out your iPhone and extending your arm for a few photos.
Unless your report or the MSC asks whether or not anyone saw you taking photos or the interaction you sustained with the owner is one (or part of one) you need to evaluate for customer service or hospitality, then you do not need to report the occurrence.
In my experience: When shops require that we do strange things that have the potential of being noticed and called out, like taking photos in a place or situation others ordinarily wouldn't or tasting every soda on the fountain or acquiring a price quote for a high-end woman's evening dress when you're a 21 year old male, it's good to have several worked-out and practiced explanations in your back pocket.