[Leave it to Benjamin to assume the best of others, but...]

Could he have been accidentally shut in the 'freezer'?

Perhaps... Somebody burnt a photograph. They were distraught, maybe, not thinking clearly. And so they went to the kitchen to have some tea and ice-cream to calm their nerves. They saw the freezer door was open, and... didn't think to check that someone was inside?

Perhaps the shattered mug wasn't a struggle, but a surprise. And everything else was... trying to warm him up again, or make him comfortable.