iPhone: erro não reconhecido do seletor

Estou realizando algumas tarefas como esta:

RootViewController
- (void)viewDidLoad {
[NSThread detachNewThreadSelector:@selector(findSomething) toTarget:self withObject:nil];
}

- (void) findSomething {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; 
doMoreThings
[pool release];
}

- (void) doMoreThings {
  doMoreMoreMoreThings on different objects
}

- (void) foundSomething:(NSFoundThing*)foundObj {
    do your stuff
}
oneObject
- (void) doMoreMoreMoreThings {
   do things
[self performSelectorOnMainThread:@selector(foundSomething:) withObject:thingFound waitUntilDone:NO];
}
-[KMLParser foundSomething:]: unrecognized selector sent to instance 0x5888080

Qual é o problema

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