I think that's the point. 'Something' seems odd and out of place, but until you investigate (i.e. interact with the object) you don't know what it is.
I agree that the guilty object out to be more obvious, though. Maybe 'waves' emitting from it, or a 'spotlight' effect that is easier to see than just turning it blue. Nothing that lasts too long, but long enough that you can identify where the (previously) hidden object is.
