My dead-out from February seems to corroborate the 'contact with food' thesis. 
We had wild temperature fluctuations that seemed to allow the bees to break cluster, eat adjacent stores, but when temperatures subsequently plummeted, in following warming events, the bees could not access the outside frames of honey or the above sugar board. Just what I observed, no causation implied. 
This was a 2 - deep hive. My 3-deep hive did not succumb,  I believe, because they could move up to warm honey stores in the 3rd deep. It was the only difference in the 2 hives, 3 deep vs 2 deep. Just an observation, might be meaningless.
Brian
53 N 115 W

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