Plex Media Server logs. If the 6 versions of the log file don’t cover the time period of the recording then you will need to wait until it happens again to get the logs.
Plex Media Server.log - current log being written to
Previous logs:
Plex Media Server.1.log
Plex Media Server.2.log
Plex Media Server.3.log
Plex Media Server.4.log
Plex Media Server.5.log
When log is full and new log needs to be created 5.log is deleted, 4.log changed to 5.log, 3.log changed to 4.log, etc.
So 4.log or 5.log might contain the time frame of the recording.