No historical DNS records on that site for us unfortunately, any other possible sites to check?
That is a random public DNS server I found on a DNS checker site that works (as it seems to be down from all the common ones like 8.8.8.8, 1.1.1.1, etc). DOMAIN can be your actual domain or the long heroku alias.
Unfortunately the Heroku issue lost us a few thousand $ alongside a few customers.