If it's more than three months, no. Roll back your system clock temporarily until the character selection screen shows at least one day left, then select him. If Battle.Net responds with anything other than the lobby, that confirms it's gone.
Did you try selecting the expired character and entering battle.net with it (into the screen where you can join games and whatnot)? If you get a message popping up that says you can't, then it's gone forever. But sometimes even though it's marked expired, if you've played the character long enough it's saved for some time longer (not sure how long) and you can still unexpire it once you enter with that character.