It's the whois for the registry, which updates "Live". As soon as the domain drops and is registered, you should be able to tell by the Name Servers that appear.
It might take a little to get use to who owns the DNS but that's about the best way.
If you didn't check the domain at Whois.sc BEFORE the drop, you should be able to see who grabbed the domain as well by simply checking a short time after the drop.
The registry whois is probally your best bet, as you can check it several times if needed.