Missed itc claim in gst?

What I have understand,
Either you have purchased good from outside India that is import, so in that case you can claim those feb,18 ITC for the current month.
Or you purchased from Registered suppliers and during the reconciliation from the date of 11th to 17th of March 2018 you had not reconciled.
In that case also you can claim in the current month sub to Annual filing. But you should check 1st whether Supplier mentioned in his GSTR 1 in the month of Feb 18 or not. If no then immediately intimate and request them to file in his GSTR1 with Tax and interest.

you can claim itc upto annual return in next year. you can put the figure of unclaimed itc in GSTR3B in the column of other itc.... And in GSTR2 it automatically came in ur months of purchase.... So don't worry about that