If the first digit is 3 (satisfies the 2nd, 3rd and 4th guesser) and the second digit is 8 (satisfies the 1st), then the third digit can be anything apart from 0, 4 or 6 (as they have each only got one correct digit).

So some possible answers are 381, 382, 383, 385, 387, 388, 389.