Sometimes they dont make it thru, normal post can be lost too, think how many miles its got to travel and how many hands its got to go through, there is going to be a small percentage that gets lost a small percentage where the authorities get hold of them.
Get in contact with nirvana though, any supplier of seeds should be prepared to send you out some more if they havent got thru.
Everything will work out fine and you be growing in no time at all.