Vista 20 - Alarm Sounded in middle of night and turned off on its own.

["KRTYSteve" <KRTYSteve@xxxxxxxxx>]

I have an ademco vista 20 with a 6150 keypad.  Have had it for about 3
years.  In the middle of the night last night, the alarm sounded for
about 15 seconds, then turned off on its own.  There was no record of
anything happening on the keypad...in fact it still had the red light
as if it was armed and ready....And nobody called us from the
headquarters.  So it's as if nothing happened, but I can't figure out
why the alarm sounded.

Anyone heard of this before or have any ideas what may have caused
this?

-Steve