Ditto here Stan. A lot of people leave their sink covers or stove covers off 24/7, and those slots are handy for storing them. Since we like the extra counter space the inserts provide when needed, we discovered we usually had at least one of the slots vacant at any one time, so it or they commonly hold a small cookie sheet for the convection microwave or other use.
Can only imagine what became of yours, Bob. I think these things were cut out of the countertop slab so to fit cleanly, but you might check with the parts boys at BCS - if anyone has an angle on them for you, it's them. 1-800-382-2597. I'd guess some RV interior redesigners, like those across the street from BCS in Bend and others, might also be of assistance.
Joel