I was IP banned on my phone for no reason from what I can tell. The account is obviously fine because I'm in it right now posting. Why would this happen? How long will this ban last?

Weird, we rarely do IP bans. Phone IP addresses are often shared with other phones on the network which is why we rarely ban them.
Can you go to http://www.whatsmyip.org on your phone and send me a message with the IP address?

Did it mention some sort of IP registry? I've run into an issue where my phone provider rotated my IP to one that someone else abused enough to land on blacklists used by many sites.

In here we have actually ran out of IPv4 addresses, so mobile phone operators actually bundle bunch of customers to single IPv4 trough NAT. In regular browsing this shouldn't matter, but if someone from that IP does something dum, then whole bunch of people get banned.

You should check that your operator is giving you IPv6 and then cycle the connection for half a minute to get new IP address.

Reminds me of this time when one day I couldn't login to an IRC server I frequented because I was given an IP address that was banned lol