GameObject active but nowhere to be found (not even in hierarchy)?

Well, title says it all.

Somehow Unity tells me there is a GameObject in the scene, with a script attached to it, which extends from MonoBehaviour. The script invokes the override Start and Update methods.

However, this GameObject is never instantiated through code, nor is it in the hierarchy (not even at runtime).

GameObject#activeInHierarchy returns true.

Any ideas of what this might be?