To follow up on this, I contacted Nutaku's social media manager about your situation and she was sympathetic. She was not happy about how your ticket was handled and offered a partial refund. You can follow up by contacting her at @nutakugames on Twitter with your Nutaku ID, which will be matched against their records.
I also polled my Twitter followers about this policy to get a sense of how such a policy might be viewed by the VN/eroge audience at large.