Finding Myrmecocystus founding chambers in the foothills is like finding a needle in a haystack. There are just far fewer Myrmecocystus nests in the hills than there are in the desert. In my experience, I probably see 30 times more Myrmecocystus nests in the desert than I do in the hills... so you can imagine what finding a founding chamber is like. It takes a lot of luck, and JasonD had it that day. I actually did get lucky last year and found one in a founding chamber in a little patch of dirt right in the middle of the creek at Ice House Canyon in Mount Baldy. Unfortunately it died. But yeah... they're waaaay easier to find in the desert when most of them fly after July.
I got super lucky. I was walking my dog and she spotted the queen. I went to see why she was sticking her nose in the dirt and the queen was there!