Camera missed motion and timeline missing 1 hour of history

Someone came onto my property within my set zones and the cameras did not record. I checked the timeline and could see this happen as my cameras are set to take a snapshot every 3 minutes. Now a day later I need to go back and view that piece of history again but it is missing. The timeline is now missing an entire hour of history. How is this possible? I can see the lapsed recording timeline for the rest of the day but the 1 hour I need to review is now gone.