I have a CentOS server that has been working well until recently.  The virtualized instance of the server encountered some type of issue earlier today and required it to be hard rebooted in order for it to be able to be interacted with again. As I was digging through some of the log files to figure out what had happened, it appears that there are a number of days worth of entries that are missing from some of the log files. For example, the messages file has information from 6 days ago and then this morning after the reboot.  I have looked through the tar g-zipped log rotated files as well and could not locate the needed information there.  I was curious if there was a different place I could look for the information?  What are some instances in which the information would disappear like this?Should I be worried about the machine having been compromised?  A rkhunter scan did not find anything.
Missing entries from messages file
logs;troubleshooting;logrotate