Reid notes that Locke's view here seems to be that no-longer existent ideas are “revived” or brought back from the purely metaphorical storehouse.  But as Locke himself acknowledges elsewhere in the Essay, no object can have two beginnings of existence — that is, it cannot come into existence at two distinct times. So there is no serious sense in which an old idea is revived.  What Locke must be committed to, then, is not the mind's ability to resurrect nonexistent ideas but its power to produce new ideas that are similar in certain respects to ideas it has had before.  So Locke must be read as saying that when we remember, our minds produce ideas that we recognize as similar to ideas we have had before.  Of course, we might take these ideas of memory to be the very same token ideas we previously had, but this is just a pre-reflective opinion that we can see on reflection is not quite right. 