I used to work in a dealer, when i was a mechanic. As far as i know, and i am sure it has not changed. The dealer gets paid either way. If it is warrenty they still get paid. It's not like they lose money because the part went bad.
I myself just do not see the point of the dealer lying. I maybe wrong, but there would be no point. Yeah you install alarms, but you do not know what the installer did. And from the pictures you really cannot tell. Either way, i would go back to S/C and bring up the matter with them. I would do the same, no doubt.