If a Memory Tablet is destroyed, lost, or stolen does the Avatar to whom it belongs immediately loose the ability to activate the powers inscribed on it?
Oh yes indeed the Avatar does lose the material contained thereon, the capacity to use it! The Memory Tablet is a harmonic key, shall we say, that enables the opening to the place from whence the Power comes, the AEPs being the force needed to “turn” that key. So when the frequency to which the Avatar is attuned is destroyed, or changed (by loss of any sort), there goes the capacity to use the activations that are recorded on it. Think of it as a sort of radio that the Avatar is able to tune mentally so as to get in the desired “station” the Power or other activation written on the Memory Tablet. A broken “radio” can not be tuned in at all. One that you can no longer mentally find can’t be operated either. Contrarily, if the Memory Tablet is gained by a character able to use the Extraordinary Ability information inscribed thereon, that individual is then empowered to utilize it as if it were his own.