If the log file grows, it's because one of these
a) you don't have log backups
b) you have replication or mirroring that are preventing truncation
c) your load is increasing to the point where you need more peak log space.
d) someone manually grew it.
Are you sure you're checking the right database in sys.databases? You are sure that log backups are on the correct database?
a) I see that the trn files are being created every hour in my backup directory - and named accordingly
b) no replication or mirroring on this server. Mirroring was setup once years ago, but then disabled/turned off
c) the load is the same, but this particular DB is transaction heavy (about 20g a day)
d) only DBA here is me, and I didn't grow it.
I verified the log backups are on the correct DB.
Is it possible that the log growth is simply due to heavy transactions? I know unchecked it grows about 20G a day. With log hourly log backups and nightly fulls it grows about 10G a week.