The idea here being that the SCP is not an object, but a quality. The affected object or person is wholly uninteresting, and those casually inspecting or following them will tend to lose interest. The effect extends to recordings and other media of the object, if taken while the quality is present.
Said object or person is not invisible, but will not attract attention, even when doing outrageous or dangerous things. Affected people can use this to their advantage, so long as the effects of their actions do not attract too much attention. What they do is uninteresting, but not the results (missing items, damaged storefronts, blood…)
The quality will leave if the object it's attached to attracts too much interest, and there is a suitably unnoticed object or person nearby. This can happen if someone actively investigates the object long enough. This would make studying the quality very difficult, let alone tracking it down.
I need to mull this one over before trying to write it, all things considered.