If such a trove did not exist the Hermanus chapter of Legends of Hermes becomes even more silly. The chapter shows an extraordinary amount of expense going in enchanted devices to detect and trap intruders all for the protection of the supplies of the Tremere. Specifically it shows the items that exist in a few rooms surrounding a laboratory where one wouldn't expect to see a great deal of loot.
The defenses in this non-loot-holding part of the covenant are deliberately non-lethal but I believe that there are hints indicating that the items in the areas where actual enchanted devices were held probably would be lethal as all get out.
Legends was written prior to Against the Dark and it takes the tack that most of the tremere enchanted device storage is at Coeris rather than the the covenant where it is detailed in Against the Dark (the crown on the mountaintop one, that has the Enchanted statue of Tremere that no one wants to risk moving for fear of being targeted by the enchantments.)
In other words, if you want to run the non-hermetic bank heist story there's some existing background that you might choose to use to plan your clever theft around.
The reason why the powers in this Talisman didn't work for Jonathan's character is that the spells were "Personal" range: wards against fire and weapons, Seven League Stride, and so on. A talisman allows Personal range powers to affect the magus. Someone else can take the talisman and use it, but the effects will only work on the talisman, not the magus, because he is not the owner of the talisman. Effects in the talisman which were NOT Personal range -- like Ball of Abyssal Flame -- could be used by anyone who knew how to activate them.
The effect Jonathan's character was given was, as I recall, a Creo Vim effect which created a "magical shell" around him. The talisman perceived this magical shell as the talisman's owner.
While the idea of Tremeres manufacturing and hoarding Talismans is cool. There should still be plenty of "left over" Talismans floating around the order from Magi of other houses particularly Boni's and Verdi's.
I try to make up a couple of interesting remnant Talismans to appear over the course of a saga.
Did the effect need some sort of link to the particular Magus, or the specific talisman? Or was the effect a general spell designed that affected all Talismans? Interesting idea.
I would think that it would require a thorough examination of the talisman to derive what the talisman is looking for. I think that if done as an enchanted device it would certainly need to be specific to matching a particular magus, I could be persuaded to go either way on a spell but the caster would have to be very familiar with the item first. Similar to the way that you can use rego vim to duplicate a known triggering action for an enchanted device but not a triggering action that you don't know.