Hope you find it. I had a "senior moment" experience once (can't claim it was the only one ever, but it is the one that comes to mind.) It was decades ago, when I was far from being a senior. I was preparing dinner and just KNEW I had purchased lettuce on my last trip to the grocery. Couldn't find it. The next time I opened the freezer -- there it was. I am convinced that we do so many things by rote that sometimes we have something in hand and "put it away" as if it were something else.
Please do tell us where it was hiding when you find it.