Wrong scale. The large voids are seen in the structure of galaxy groups, hundreds of millions of lightyears. Technological disasters would make holes in individual galaxies.
Of course the most likely tech disasters would be invisible at distances of a few lightyears, not massive conflagrations of stars.
Paul Schauble wrote:
> Perhaps we have observed the holes. Astronomers have found huge
> voids with few if any stars and are now describing the universe
> as a soap bubble foam with the stars concentrated in the bubble
-- Doug Jones, Freelance Rocket Plumber