I think the 'pronghorn' defines a particular size (5-6 inch blade?). I think Ed forges 52100 exclusively now, so an older piece with a damascus blade would make it more valuable. In addition, his signature handle material is sheephorn (there is an amusing story behind that).
If it has a blade in that size range, with a sheephorn handle, made from 52100 steel, it would be worth around $1000 depending on condition. I have seen smaller, and larger Fowler blades in the $600 to $1200 range.
Something like what you describe would be particularly collectable, especially if it has a handle material that is Not sheephorn. As to value, I really have no idea. There are very few Fowlers offered for sale on the secondary market. I would have to guess in excess of $1000, but I would need to see and handle the knife first. Many people buy Fowler knives as users, since that is the whole purpose behind Ed's knife design's.
If it is still there tommorow, at least try to take a picture and share will all of us. I would love to see that knife.
Paracelsus