MSSQL 2016 Server: All databases marked Recovery P

Question

Tonight I had run into this issue where all my databases on our production server were in a Recovery Pending state after doing a Windows (server 2016) Update, an update to my Redgate SQL Backup software and restarting the server. Looking at the logs I found that all of the databases were not accessible with an "Access denied" error. So I figured it was something to do with the user under which the MSSQLSERVER service was running. So I explicitly set permissions to the data and log folders for that user and restarted SQL Server service and all is fine again.

HOWEVER, this server has been running for a very long time - and I have not seen this kind of issue where suddenly the user doesn't have access to the data and log folders. SOMETHING had to have removed permissions on those folders. In addition, now when I look at the security tab of those folders, I see that the user I'm using to run the MSSQLSERVER is explicitly defined. But on our staging server, which has the exact same configuration, I DO NOT see the user explicitly defined there, yet the server is running along just fine.

SO - To my question. What the heck happened? Any ideas? Should I be worried that the user account running my MSSQLSERVER service is now explicitly defined in the Security tab of my data and log folders?