In my years of experience with Amazon.ca and many frustrated moment in the situation you mention, most probably if no slip cover it's because it doesn't come with one. But i've been surprised and sometime received one.
On the Other Hand, if you see a picture with a slip clover, it doesn't mean that you will receive a slip cover(even if new new release), very often they just ship the amaray I think it's called, the plain blue plastic disc holder ?
I complained many many times, and they never did any changes, they said they have no control over it, they put the picture that the distribution company gave them (for example with a slipcover) but if the company ship them something different than the picture it's not their fault. But that I find a ridiculous answer, if they receive a product when shipping they should in their computer(shipping dept) have the picture of the item we ordered the one they are shipping, and if they see any discrepancy we should be informed before they ship us something else(i.e. missing slip cover).
But Amazon.com is much better organized, ever since I switched, this type of issue rarely happens, it's the opposite I find. often it's just an amaray picture but I end up receiving a slip cover with it.