The reason why expressing the connection between not having a mate and seeking a mate in terms of PCT is so difficult is because "not having a mate" is not a perception, and because "seeking a mate" is not a behavior. Rather, these are an abstract world state with multiple perceptual correlates, and a broad class of complex behaviors that no known model explains fully. Given such a confusing problem statement, what did you expect if not a confused response?

The second problem, I think, is that you may have gotten a somewhat confused idea of what (non-perceptual) control systems look like. There was a series of articles about them on LW, but unfortunately, it stopped just short of the key insight, which is the PID controller model. A PID controller looks at not just the current value of its sensor (position, P), but also its recent history (integral, I) and rate of change (derivative, D).

If you want to test PCT, you need to step back and look at something simpler. The most obvious example is motor control. Most basic motor control tasks, like balancing, are a matter of generating some representation of body and object position, figuring out which neurons trigger muscles to push it in certain ways, and holding position constant; and to do that, any organism, whether it's a human or a simple invertebrate, needs some neural mechanism that acts very much like a PID controller. That establishes that controllers are handled in neurology somehow, but not their scope. There's another example, however, which shows that it's considerably broader than just motor control.

Humans and animals have various neurons which respond to aspects of their biochemistry, such as concentrations of certain nutrients and proteins in the blood. If these start changing suddenly, we feel sick and the body takes appropriate action. But the interesting thing is that small displacements which indicate dietary deficiencies somehow trigger cravings for foods with the appropriate nutrient. The only plausible mechanism I can think of for this is that the brain remembers the effect that foods had, and looks for foods which displaced sensors in the direction opposite the current displacement. The alternative would be a separate chemical pathway for monitoring each and every nutrient, which would break every time the organism became dependent on a new nutrient or lost access to an old one.

Moving up to higher levels of consciousness, things get significantly more muddled. Psychology and clear explanations have always been mutually exclusive, and no single mechanism can possibly cover everything, but then it doesn't need to, since the brain has many obviously-different specialized structures within it, each of which presumably requires its own theory. But I think control theory does a good job explaining a broad enough range of psychological phenomena that it should be kept in mind when approaching new phenomena.