I don't understand the urge to do public shaming instead of first reaching out to support. And the OP is so rude.
I don't know. I'm always confused when social media accounts ask to report issues over different channels when it's so much easier to just reply to customer and ask for additional (non PII) information there. In this case it's unlikely that this was the only or even first report about this issue. So why place the initial burden on a paying customer? If your social media is just a marketing channel, at least make that…
Is this snippet from their Twitter bio clear?
"If you need assistance, please submit a ticket: http://fastmail.com/support"