Here's a link to a photo of the box: http://www.flickr.com/photos/jasonlie...
On March 25, 2012, Kellogg's responded to my email inquiry:
"Thank you for contacting us regarding Sunshine® Yum Yums.
"Unfortunately, stores only want to stock the fastest moving products. If the stores start to discontinue an item, we find that we cannot produce the smaller volumes the business demands. It is always difficult for us to make the decision to discontinue a product, as we know it is always someone’s favorite. At this time, there are no plans to reintroduce it.
"We know that it will be hard to find a replacement, but we are always developing new products so we are sure that you will soon find another favorite! You should try Keebler® Country Style Oatmeal cookies with Raisins."
I don't think Keebler® Country Style Oatmeal cookies with Raisins will satisfy my hankering for Yum Yums.