When I asked above, I was thinking about the problem of locating someone who you know well, but you just have no clue where they are. Something along the lines

When I asked above, I was thinking about the problem of locating someone who you know well, but you just have no clue where they are. Something along the lines of nationwide decades-long hunt for the Unabomber, but in an alternate timeline where 1. his identity and his DNA (or his brother's) were known, but his location was not, and 2. he did not live in an off-grid cabin, but instead somewhere connected to a wastewater treatment plant, or regularly showed up in one. It's a far-fetched scenario, but I don't know enough about the breakdown of DNA in wastewater to know if it'd be possible to locate him via this method. If he wasn't shedding a unique strain of a virus, let's say, but where his genetics are known. This researcher explained to a reporter how they conducted a binary search of sewer lines from the treatment plant, all the way back to a single manhole which was only fed by a single employer with 30 employees. I just don't know if this is only possible using viral RNA, or if anyone's DNA would be possible to search on in a similar manner. For good public health reasons, we're likely to have continual wastewater surveillance at all major plants going forward - I just don't know how far it could be pushed.