Simon bar Kokhba
The quote from Rabbi Akiva, however, should probably be understood in light of his disappointed belief that Simon ben Kosiba (surnamed Simon bar Kokhba) was the Messiah who would liberate the Jews from Rome, return the lost tribes and usher in the long-awaited Olam Haba. The failure of the Bar Kochba rebellion convinced Akiva that the lost tribes would not return at "that" time. It is probably a mistake to take Akiva's statement as a categorical denial of a return at any time.