The thing is, you don't need a lot of extra heat to melt a chocolate bar on your pocket. It's perfectly possible that everybody felt hot when working on an active radar, but didn't discuss it or maybe even notice the correlation.
Oh wow it's even known what brand of a bar it was, funny that.
> The first food deliberately cooked with Spencer's microwave oven was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.
https://en.wikipedia.org/wiki/Microwave_oven#Discovery
The thing is, you don't need a lot of extra heat to melt a chocolate bar on your pocket. It's perfectly possible that everybody felt hot when working on an active radar, but didn't discuss it or maybe even notice the correlation.