The way I read this it seems to me that the person that contacted Cliff Carter Knives wasn't even the maker that Cliff's knife was similar to.I drew up a design recently and was notified by another maker that it looks very close to an existing model of another maker.
So far the few knives I have designed and made have all drawn off of handles, blades, shapes, ideas and looks that I like in other knives. My designs have been hybrids of two or three elements that were put together and then adjusted until I decided I liked the look. Even with that process I found a rather similar bird and trout on the internet to one I made a couple years ago.