So where is the treasure?
We don’t know. We known from both Josephus and the Arch of Titus in Rome that Roman legions pillaged the second temple and carried off valuables. The relief carvings clearly show various Jewish relics being paraded through the streets of Rome. We also know the loot from the temple funded the building of the Colosseum. Therefore, it is safe to assume that a great deal of Temple wealth was sacked.
Romans were not nice people
Don’t fall for the romanticized image of civilized Romans lounging on stone sofas. Primary sources show they were a bloodthirsty lot, and society feuds often ended with one family killing off entire families. This aggressive code of conduct can be expected in the army legions as well.
Josephus wrote in Jewish War about soldiers who captured refugees fleeing the siege of Jerusalem. They would slit the refugees open searching for coins they may have swallowed before the refugees fled Jerusalem.
It would be expected that once the legions found out about hoarded treasure (Temple or otherwise) that torture would be employed in the search of it. So I expect most of the treasure was recovered….but not all of it.
Jewish defenders were renown for resisting Romans. It is quite likely that enough minor caches were made that some escaped the Romans or misled them to a cache already forfeited, thus a treasure hoard may still be cached in the earth.