I'll hazard a guess that he was in the BULK hold - not the main cargo holds. Its common practice for one handler to be in the bulk hold to manhandle loose bags into position. Theres little need for a handler to be in the main cargo bays as the bags are loaded by igloo, and the whole process is mechanized.
I'll also hazard a guess that this hero was having a snooze on some comfy bags, and his mates either forgot him - or 'forgot him' (if you get my meaning). Maybe he's not popular with the lads?
Bulk holds in A330's are heated. Animals (dogs/cats) are regularly carried in the bulk holds of Airbusses.
So no big deal - he'd have lived to tell the tale even if he wasn't found until NY.
Unless he has a very good excuse - the fecker should be sacked for falling asleep on the job, and endangering an aircraft.