They can probally hybridize I Produced some C. Lancolata X C. Grandiflora "Sunray".

I see no reason why they could not produce viable seed, but that isn't the reason the 'Limerock Ruby' is missing.
It's because 'Limerock Ruby' is hardy to only USDA hardiness zones 7-10, and therefore is not hardy in your climate. The producer of the plant originally marketed the plant as being hardy to zone 5, but after one winter out on the market all plants in zones 5 and 6 died.
The problem occurred because a greenhouse in MI, that was paid to test the plant, kept the plants in a climate-controlled greenhouse all winter, and not out in a field where they would have been affected by the elements.
The nursery that I manage wintered-over 100 starter plants in one gallon containers, and all of them died.

-Jay

My own theory:
The supposed 'Limerock Ruby' plant I bought and grew (and loved) last year looked EXACTLY like dwarf red plains coreopsis (Coreopsis tinctoria red), as did the entire stock of it where I purchased it. They did not look at all like the pictures or descriptions I've seen in other catalogs of LR.
If it was indeed that, that species is a native annual, which easily explains why the plant did not come back. However I don't see any seedlings either.

My similar-structured 'Sweet Dreams' plant came back quadrupled in size. Just huge. It is right next to where the LR used to be.

Here is a link that might be useful: picture of C. tinctoria red (at bottom of page)