That is quite unfortunate.  Assuming things happened as you said, there needs to be some sort of accommodation such as provisional ballots.  It could have been an honest mistake or bureaucratic error, and it's also quite common for individuals and political parties to tamper with elections using various techniques such as manipulating lists of registered voters.  False claims of disenfranchisement are also a common occurrence, though I am not insinuating that is the case here.  Those who believe genuinely that they were disenfranchised should seek redress with appropriate authorities.