And never have.
Not 'bearing false witness against thy neighbor' is right up there with 'thou shalt not steal'
It was in Rome until the 5th century - and the official religion of Rome was Christianity from the time of Constantine forward (and there was basically only the Catholic Church at the time), plus it is **according to this article** held in a monastery.
So I, a non-Christian, have assumed that either Christian Rome or a monastery (which is usually full of monks and/or priests and/or nuns, etc. - all Catholic religious figures in my mind) are both associated with the Catholic Church and also had possession of the objects in question. If that's a mistake, so be it - and I'll gladly stand corrected of my ignorance. However, such ignorance (IF I'm completely wrong) does NOT rise to the level of bearing false witness. That (i.e. lying) requires that I know the truth, but purposely don't speak it and/or speak an untruth with the specific intent of deceiving someone.
IOW, please be careful with your own accusations or assumptions.
Rome was conquered and looted more than once in the 5th century. One or more of those barbarian armies took your treasure, if it was even in Rome by then to be taken.
plus it is **according to this article** held in a monastery.
Read it again. It doesn't say it's "held in a monastery" but buried under a monastery. And the monastery in question is not Catholic, but Greek Orthodox.