Yes, you are right, once the VRM is erased it is gone for good.

Though it is possible to test only a fragment of an object, but I do not know if the instruments that were used were sensitive enough to work with only a very small chip, which could be glued back, afterwards.

Many such ancient pottery objects are already broken, so they must be glued anyway, if a restoration is desired.

It strikes me as risky, if the item is in any way delicate or has absorbed water at all. But I'm no ceramics expert!