The Chinese military used a similar method to find US spy planes - they used background signals from e.g. cell phone towers and looked for the area where there was a "blank spot" - which was the spy plane's absorption of the spectrum.
This is a popular hypothesis, but how exactly do you think it may work? It's not like you can see a "blank spot" by looking from radio sources, you'd need to put your antennas in a position where the plain will intersect your line of sight to the transmitter. And not just one, but massive number of lines if you plan to track it and deliver a missile there.
It sounds pretty improbable and I believe it's just an urban myth.
Guess what emits UHF/VHF? Terrestrial TV stations and 900Mhz and 700Mhz cell phone towers , like Sprint and Nextel used to operate in the USA before their spectrum was traded/sold back to the government.
It's well known that low frequency radars can detect stealth airplanes. But it's difficult to target a missile using them, and they're too big to put anywhere but on the ground.
