Nature:
Do you have any more picks of the duck? What color was the bill? I believe a black hen is a kinda greenish/olive, I know the male is a yellowish. A hen mallard would be orange black.
The white speculum border would definitely be a sign, to me at least, that its is for sure a hybrid. If it had a black duck bill (yellow or greenish), and had the white speculum border, I would say you had yourself a hybrid. VERY cool. Exceptionally cool that is was your pup’s first retrieve.