Well, I had an experience similar to eyeing the give/take a penny cup at the store. We recently went on a short family trip to St. Louis. While there we visited the City Museum. Which, BTW, is a very unique and interesting place and a blast for kids. Anyway, we were in the gift shop and I was admiring the floor, which had a lot of tile mosaic work. Then it finally dawns on me what vast parts of the floor are. There are coins embedded in the grout! There are pennies, nickels, dimes, quarters, half dollars, even some Sacs. I did not get on my hands and knees and eyeball dates and mintmarks but who knows what might have got stuck in that floor. Oh well.
If there were Sacs, then it sounds like a recent project, and hopefully doesn't contain many rare coins. By "rare", I mean pre-1964.
Well, rare in the sense that I almost never see pre-1964 in pocket change. I figure if he's seeing Sacs in the mortar, the chances of his finding a SLQ are poor.