Got this email that proofs our concern:
We had some login issues this week that may have caused you to get logged out of Twitter on your mobile device and not be able to log back in.
We've now fixed the problem, and are really sorry for any inconvenience this may have caused.
Click below to log back in to Twitter using your username and password, or just go back to the Twitter app on your mobile device and do the same.
Thanks for using Twitter, and have a Happy New Year!