Conjuration magic is specifically referred to as the summoning of creatures or items from another plane of existence, so it would be possible to imagine storing items in some small demiplane of Oblivion (which we know there are innumerable amounts of) to then conjure forth as needed. How proficient a mage has to be in Conjuration magic to be capable of this, however, is another question entirely, but I do not think just about any novice would be able to do it.

On a tangentially related note, the Overlord light novel series provides an interesting solution to the conundrum posed by notyuu, though from a slightly different perspective. In that series, healing magic that is used to, say, regrow a lost limb causes the original limb to disappear. However, if the original limb has been transformed/processed enough so that it no longer constitutes as a "limb", such as by being eaten by a monster and digested, it (or, in this case, the nutrients, energy and waste it turned into) doesn't disappear. We don't know if any of the Earth Bones govern this specific aspect of magic and natural laws, but if similar logic is found, then that might be a sufficient answer.