I don't think that is the case. For some reason, I also was logged out of musing. But when I tried logging in again, I had to give permissions to musing app via steemconnect again.
It may have been caused by one of the two following reasons:
1. Musing revoked all the steemconnect tokens that provide it with various levels of permission of steemit accounts. Doing this requires users to login again because it logs them out automatically. You may have faced an issue while logging in again.
2. Steemconnect issue. This is more likely and has happened with many other apps as well. If there is a issue with steemconnect then musing will fail to work properly. This kind of problem did happen recently with musing too! But musing is not at fault for this kind of problem because it is something that happens in steemconnect's end. This kind of issue generally dies within a day or so after the problem is fixed.
The most likely reason you had trouble logging in is Steemconnect, the service you use to connect your Steem account to other platforms, was having node issues, making it so people couldn't connect and log in.
I haven't had trouble with musing. A little bit ago I had trouble logging into steemfollower though.