Sounds like she was sleeping.
I tend to startle my corn when I change her water, and she's curled up asleep underneath. When I go to put the bowl back over her she usually flinches because of the shadow over top.
P.S.
My corn snake has a large dog water bowl, that has a hole cut out in the side for her to get underneath. It doubles as a cool hide, and it's her favourite... especially since she lives beside a ball python and underneath a blue tongued skink.