I know that not all Silkie crosses have crest, feathered feet, or 5th toes. Just pointing out that a crested chick would rule out all non-crested parents, leaving only the Silkie as a possible father.
It is possible to get a single comb chick from a father with a walnut comb, if the walnut comb is P/p+ and R/r+
But if you know they are pure PP or RR or both, then I agree they cannot produce a chick with a single comb.
Then I agree that rules him out too.
Do you know if he is heterozygous Dominant White or homozygous Dominant White?
What leg color from the American Game side of the cross?
Because if he is split for Dominant White/not, then depending on the leg color genes he might also be able to produce a chick like the one you showed.