It makes sense that they were only sold at Sam Andreas, which is gone now. I did have one on my first trip or two - it was one of those CA-specific things that made all kinds of sense, and I'd only had them in the Indio area; seems weird more places in SoCal didn't sell them (and I imagine SOME did, but no place I ever went), because a good date shake really is VERY good. The ones at Sam Andreas were pretty good. I've had one or two in Indio that were heaven in a glass, though.
Just out of curiosity, what were you doing in Indio? It's not the type of place that most people visit, unlike neighboring Palm Springs or even Riverside. I think the only times I've ever been there was just driving through, or maybe stopping for gas along the way
When I was a kid, my family used to like to camp in the desert, and we almost always would stop in Indio for a date shake. As an adult, if I was ever in Palm Springs I'd try to get one too - it's really not that far, and worth it to get my "fix."
Palm Springs Traveling: California 2016 - Part 16 Back in Vegas Traveling: California 2016 - Part 17 Our Last Day in Vegas Traveling: California 2016 - Part 18 Flying Home Traveling: California 2016 - Part 19