Did You Forget to Count?
One who forgot the whole night to count, should count in the day without blessing, and on the following night count with a blessing. If he also forgot (to count) during the day, he should count afterwards all the nights without blessing. If he is not sure if he counted at night or not, even if he did not count the following day, in any event he can count the remaining nights with the blessing. (KSA 120:2)