There are very specific and extremely well-considered (from the retailer's side!) reasons why every single SKU in a supermarket is located where it is. For an in-depth study of the topic check out Paco Underhill's book 'Why We Buy: The Science of Shopping'. Broadly speaking, retailers will change the location of certain products for reasons embracing, because those products are not selling off the shelves fast enough in their previous locations; because different times of year and topical occasions require the showcasing and upfronting of seasonally and topically specific products that can be expected to sell faster accordingly; because the manufacturers of specific products do deals with retailers based on in-store location; because retailers are constantly studying traffic flow and purchase patterns within their stores and constantly looking to improve sales by reorganizing layout and flow. They will change the signposting of different product sections accordingly, but can also be not too concerned about your frustration with wandering around looking for certain products, because that can stimulate more impulse purchasing - so, as per Oren's answer, the risk of you walking out without purchasing is one they're prepared to take.