What if we took a page from aircraft and did the opposite? You'd be hard to spot on a thermal sensor if you sprayed superheated chaff in every direction.
The moment you maneuver, you'll pop out of your cloud as all your chaff keeps obeying Newton; they'll know exactly where you are and how you'll move. Project Rho actually discusses the idea of decoys. I don't necessarily accept that a decoy must have a power source comparable to the ship to have the same radiation and heat signatures as the mother ship (as long as your decoy is unpowered - decoys that try to "solve" the maneuver problem quickly run into the issues outlined), but you do need to worry in such a case about your decoys also having endurance.
Basically, stealth in space is maskirovka - you don't hide yourself completely, but rather as something else. This has parallels to the real world - a stealth bomber on radar is more of a sparrow rather than an outright hole. Your fancy warship, by thrusting at lower vectors, looks like it has less engine power than it actually does, perhaps more like a freighter of similar tonnage. I agree that Project Rho makes multiple assumptions, but these do not seem to be entirely unfounded to my eye. The reason for stealth being harder for man-made objects compared to natural objects is, as noted, temperature; they note present-day capabilities to detect such man-made objects and make assumptions that these will only improve in the future, while tyranny of the rocket equation will persist (that is, detection will be effectively instantaneous if it takes you hours to identify a ship on a trajectory best measured over weeks or months).
Man, I wish they'd do one of those full scans and give me a complete list of objects in orbits similar to earth already.
The problem with your little implication is that natural NEOs have had just a wee bit of time to cool off and no internal thermal generation to make them stand out. By contrast, people like to live at temperatures a bit above that of the interplanetary medium, and even chemical thrusters fire at higher temperatures than that as well.