I also used to like that Golden Grain Macaroni & Cheddar, used to buy it all the time. I often wondered what happened to that product. All of a sudden one day it was gone. Nowadays, the boxed Mac & Cheese I buy is from Kraft.
The best frozen Mac & Cheese is Stouffers. Back in the 70's, there was a frozen Mac & Cheese made by Creamettes that I used to like, but that product is long gone too.
A couple discontinued Pop Tarts flavors I miss are Frosted Grape and Frosted Dutch Apple, also Frosted Chocolate Vanilla Creme. I know sometimes Pop Tarts brings flavors back for a limited time, I'm hoping these flavors make a comeback. They have a new limited one, Frosted Blue Raspberry, I haven't tried it yet.
The grocery store near where I live no longer sells a few breakfast products that I like. I think the products are still being made, it's just the idiocy of store management that decided not to stock them anymore. The products are:
Toaster Strudel Raspberry
Toaster Strudel Boston Cream Pie
Toaster Scrambles Bacon & Sausage
There is a Wal-Mart here also, I'll have to check there and see if they have these products.
Another product I miss that also seems to be long gone from stores are these frozen banana cream pies with the graham cracker crust. Haven't seen those anywhere in years, they were tasty.