The Miu Miu Bag/Satchel has been discontinued. I have asked at many different Miu Miu locations and different SA's have confirmed it. Some stores do have the Bow bag in stock. And as far as I know it's not on sale on the official Miu Miu stores. I was also told that Miu Miu discontinued the Bow Bag because the company wants to move in a different direction. Miu Miu is experimenting with different (and more luxurious) leather finishes as well as different styles.
The Coffer, however, is not discontinued, though I can't guarantee that its design is not going to change. There is indeed a new coffer as part of the Biker line, which is a bit different from the Matelasse version we are used to. All in all, with the Cloud bag and the Vitello Soft Miu Miu is moving in a better direction.