The Urim VeTumim
The Urim VeTumim served as a vehicle to communicate with G-d. It helped answer such questions as whether Israel should go to war, how the Land of Israel should be apportioned among the various tribes, and whether the city of Jerusalem or the area around the Holy Temple should be expanded.
There are different opinions as to precisely what the Urim VeTumim was. Some say that the term refers to the precious stones of the Breastplate (Choshen), while others maintain that it refers to the ineffable name of Almighty G-d (Shem HaMeforash) that was kept between the folds of the Choshen.
Many do not include the Urim VeTumim among the eight garments that the Kohen Gadol was required to wear. However, the Rambam does include it. This leaves us with a serious question. During Second Temple times, there was no Urim VeTumim. This is stated by our Sages and confirmed by Josephus (1st century BCE), who states that “The Urim VeTumim disappeared two hundred years before I wrote this book.”
If this is the case, then according to the Rambam, how could a Kohen Gadol have served in Second Temple times? It is forbidden for a Kohen Gadol to serve without the required eight priestly garments.
A possible explanation is that the Urim VeTumim did exist during the Second Temple period, and was worn by the Kohen Gadol. What changed was that it was no longer a conduit for divine messages. Josephus’s words could be understood as indicating that the Urim VeTumim no longer had the power it once did. Alternatively, it is possible that the masses were not aware that the Urim VeTumim still existed, and that included Josephus even though he was a Kohen.