Forgot to add salt to french fries while soaking it in hot water
Any salt added during the soaking step won’t make your fries significantly salty, during blancing the potatoes will precook and absorb some water and if salted, some salt (a 3% brine is suggested here). But the average French fry recipes I am familiar with typically don’t salt the water and many don’t parboil. - I never salted any soaking water and still got good results. 

Fries are usually salted (or spiced, if you prefer) right after the last frying step when the remaining frying oil helps the salt stick to the fries.

In short: Yes, there are sources that insist on salted blanching water, and maybe it’s the way to perfection, but if you didn’t, simply salt afterwards.