Amazing, the knowledge acquired, distilled and shared to enable this is just wanted immense. My father had a major bypass op 6 years ago and I remember him saying how he felt when he first awoke after the surgery. He mentioned feeling cold!
Those heated blankets they have in post-surgery rooms are very nice...
WRT the hypothermia, you may have been slightly hypothermic as a result of having so much of your body surface exposed to the air. People don't realise that ambient temperature (18-22C) is actually quite cold in relation to body temperature (36.7C) - it's only the fact that we wear clothes that means we don't feel it.
Nowadays we have heated blankets in theatre too, to offset this heat loss.