While that sounds like an interesting tidbit, it also doesn’t appear remotely true based off of the history sections in the wiki pages for microwaves and microwave ovens.
> In 1945, the heating effect of a high-power microwave beam was independently and accidentally discovered by Percy Spencer
Sure, meanwhile using microwaves to heat stuff up dates back to the 1920’s. WWII soldiers would regularly stand in front microwave equipment to warm up. The resonant-cavity magnetron was a British invention that finally made microwaves far more efficient to produce.
The story about noticing a candy bar melting in his pocket is also kind of funny as that’s what normally happens to candy bars in your pockets, further it means he didn’t notice he himself warming up.