i'd understand if it was a dress shop or something, where you could be taking a photo of an item to then go away and have it made/sew it cheaper.... i'm thinking more like bridal shops where they need to protect their products etc
however, just a run of the mill shop ie a camping or major furniture shop, well i just click away! we do it to show each other like you and also to compare prices, check the pic when we get home to see if it suits etc.
I would have challenged the staff member why you couldn't take a pic? and what difference was between the product on display and catalogue. and if they weren't helpful I would have said, Okay, I'll buy online/elsewhere then. I don't think taking a pic is really different that writing down the details on a piece of paper so bah.