It's happened to me when I purchased from Burberry. I saw the coat I wanted online so went to my store to buy it. It was only when I got home did I realize the trim on the collar was different and I liked the version in the photo much better (even to this day). I asked Burberry to investigate if I bought the right coat and when the answer was yes, I asked why the photo showed a different collar (it had no trim).
Their response (after investigating for a few days) was, the stock photo is taken months in advance before the product is put into production. During production, the QA team looks to see what changes should be made to provide a superior product. In my case, they felt the coat needed a trim so the collar could retain its shape. But, Burberry forgot to take a photo of the post production coat and so the website didn't represent the actual product.
Their response (after investigating for a few days) was, the stock photo is taken months in advance before the product is put into production. During production, the QA team looks to see what changes should be made to provide a superior product. In my case, they felt the coat needed a trim so the collar could retain its shape. But, Burberry forgot to take a photo of the post production coat and so the website didn't represent the actual product.