This reminds me of a plot twist from Gundam 00, where a device whose nature is absolute radar stealth via radio absorption is detected by flipping the situation

This reminds me of a plot twist from Gundam 00, where a device whose nature is absolute radar stealth via radio absorption is detected by flipping the situation: Saturate an area with radio waves and look for silent spots, the stealthy Gundams thus sticking out like sore thumbs.