When breeding two Pokémon, same species or otherwise, the mother MUST have the hidden ability in order to pass it down, otherwise the offspring will never get its hidden ability. For example, if breeding a male Growlithe with a female Vulpix, the father Growlithe's ability doesn't matter, and the mother Vulpix must have its hudden ability, Drought, in order to pass it down to its offspring. Or in your case, the female Froakie must have Protean in order for the offspring to have a chance at getting it.
Edit: The male Pokémon, when breeding two of the same species, also has a chance of passing down the hidden ability, but the chance is much more slim. This doesn't apply when breeding two different Pokémon, however.
Source: knowledge and experience