Generally speaking, it's not the customer's job to win over the retailer. Sales people and owners who behave like that are shooting themselves in the foot. They need to compete with online retailers-- sure. So they're going to have to do that by being more pleasant and more supportive environments, by offering things that online stores can't, and by winning the buyer's loyalty.
Think how that scenario could have gone. Sales person notices you using phone camera. "Can I assist you with anything?"
Buyer "No, I just wanted to record this information so I can figure out how I can use this fabric which I love. Gotta go home and look through my patterns to see what kind of yardages I'd need."
Salesperson: "I hear you -- that is such a lovely line. Would you like me to cut a small sample for you so you can see what you have in your stash that coordinates? Also, we have other prints over here that would be amazing in combination. Would you like me to put your name on a mailing /call list so I can notify you when we get the next shipment of this line? It's very popular, and we find that we're selling out the bolts within a week or so."
Alternatively, the sales person could offer asssistance by looking up patterns online and seeing yardage requirements for you then and there.
I love a good brick and mortar fabric store as much as anyone, but if they want to survive, they need to keep up with the changing markets and the shift in how people shop.