The majority of kids diagnosed with CF have no family history of the condition, that's the thing with recessive conditions.
Absolutely, and that alone isn't evidence of someone not being a carrier.

DW's family has the recessive albinism gene. There is no history of it at all in any of her family branches, but her grandparents produced 2 out of 3 kids with the disorder, and since that time it has not reappeared. You just don't know until it happens, or in the case of CF where tests can be done.