Yes it is a very common mistake. I have worked in attendance before becoming registrar..and I have given a few "heart attacks" myself..lol...but that is with junior high and going to 7 teachers...isn't your son with only one teacher all day? Looks like that would be a little harder to mistake..but sure it happens..
We count absences in the first 2 periods for the absentee report. The rest of the periods teachers just do roll call but do not have to report it to the front office.
After all you have been thru I am sure it just magnifies the horror for you! Seems like Jaden has had more than his share of school mishaps!!!