Osama-specific PCR

We now know the human genome sequence (mostly).
We also have a good idea of which bits of it vary from person to person.
We can also infer the genomic sequence of a specific individual from the sequence of his descendents (with a bit of statistical luck).
We ought therefore to be able to infer the genomic sequence of Mr. Bin Laden if we throw lots of money at it, and have access to a few of his descendents.
We ought, with a few million dollars of investment, to be able to find those very, very, very few alleles which are specific to Mr. B.
It is also possible to amplify, detect and sequence single, chosen DNA molecules using PCR
Ipso facto, we ought to be able to develop a highly sensitive Osama- specific PCR test.
Also, If Mr. B is still alive, he is presumably still peeing
Hence, Mr.B's pee (along with millions of sloughed cells full of Mr. B's DNA) is finding it's way into some sewer, some stream, some river, some ocean.

So. Sample the water from the outlets of the major rivers around the world. Test those samples with Osama-specific PCR. One sample comes up positive. Move inland, and sample the waters from each of the tributaries of that river. One comes up positive. Head up the tributary, sampling the water from each stream that feeds it. One comes up positive. Ultimately, you can trace your way all the way upstream to Mr. B's urinal. Problem solved, and hundreds of molecular biologists employed.