Yes: it is possible to bring back the lost memory, but this only if you have obscured only a part of it, in the event that a person is forgotten by all his memories the spell would be irreversible. With all the information I have collected, the controversies and the hypotheses I am not sure what I am about to write but ok; The finished spell of incantatem should be able to return the memory, so in this case the memory would be darkened not removed and therefore it is likely to work with a not very high power of oblivion.