It is not unusual to have no entries in the unbound log if you are using the configuration variable verbosity: 0 (means no verbosity, only errors). If there are no errors, there are no log entries.
unbound.log filesize is 171418784 today. i had thought i would see several compressed log rotation files but they are empty. your reply was very useful anyways, thanks. i'll have a look at the unbound config in /etc/rotate.d per @deHakkelaar suggestion.
thanks. i do believe that is where the issue is after looking at the config. i'll check the man and find my error or come back here if i can't find it.