Fog of war. No conspiracy.
Don't most security videos usually have a time stamp on them?
If so a look at your watch would show a discrepancy.
Or perhaps no time stamp makes it easier to edit/delete tapes that show student behavior that could jeopardize your Federal grants. /s
Yes, usually in tiny print on the screen. Date, hour, minutes, seconds. I'm sure it was on the screen. Having also reviewed vids under stress, the brain doesn't function like sitting on an easy chair, eating cheetos, watching an HD monitor and freeping. Unless you are the one operating the controls (play, rewind, slow mo, reverse), it's confusing. And trying to pinpoint an AR shooter in a school, with a room full of wound up cops trying to find him, going nuts, all shouting and telling you what to do at the same time...the simple answer is ooops. Nothing more than that. Been there, done that, lower stress situation. It's easy to do.