This is an outlier, highly unlikely, but you might check that you don't have an anti-scripting tool in place that is tidying up for you. I can remember one case, a few years ago, when I scratched my head for some time over a similar problem and it turned out to be that an add-on to my own browser was interfering. Like I say, not likely, but it got me once. Bruce's points are more likely.
Best, Marv
Marvin Waschke