It’s not Lupus
Lupus is a disease characterized by having an large variety of symptoms that mimic many other diseases. To risk killing all of the humour, the joke “It’s not Lupus” is said in reference to the fact that everything looks like Lupus, so it’s not a useful suggestion.
Search and Rescue
SAR is sometimes like a episode of House in that those episodes use the scientific method. A theory is proposed, the theory is tested, repeat once or twice, and eventually the solution is found. SAR uses search theory, and we assign people to search areas using different techniques based on how likely it is the subject is in that area.
Each search of an area is a test of the theory. There can be false positives (we find someone, or a clue, that does not lead us to the subject), and there can be false negatives (we don’t find anything, but the person could still be there), and there can be misleading data (the searchers didn’t search the area properly, or went to the wrong place).
Whenever we have a particularly difficult search, someone always floats the theory that the subject wanted to disappear and has faked their death in order to escape a bad debt/unhappy marriage/ugly pets. This is when I pipe up and say “It’s not Lupus”, and then they throw me out of the command truck.
Proposing that the subject is not in the area is a theory we can’t test, and is useful only in the event that we can expand the area to include a new search area, or if we can prove conclusively that they’re somewhere else.
For example, I’ve searched all night for someone who went home to someone else’s house. Although it was never a theory in the search, there’s always some possibility that a subject is in the “rest of the world (ROW). We continued to search until the subjects called to tell us where they were. We don’t stop until we find the person, they show up elsewhere, or we run out of resources and reasonable places to search.
We can’t prove a negative in this case. We can either find the person, or give up.
Suggesting that the person is faking their death, while an interesting theory that makes for some good movie plots, is like saying that the patient has lupus, and it’s never lupus (except when it is).