From CatholicEducation.com's history of Lent:
Since the earliest times of the Church, there is evidence of some kind of Lenten preparation for Easter. For instance, St. Irenaeus (d. 203) wrote to Pope St. Victor I, commenting on the celebration of Easter and the differences between practices in the East and the West: "The dispute is not only about the day, but also about the actual character of the fast. Some think that they ought to fast for one day, some for two, others for still more; some make their 'day' last 40 hours on end. Such variation in the observance did not originate in our own day, but very much earlier, in the time of our forefathers" (Eusebius, History of the Church, V, 24). When Rufinus translated this passage from Greek into Latin, the punctuation made between "40" and "hours" made the meaning to appear to be "40 days, twenty-four hours a day." The importance of the passage, nevertheless, remains that since the time of "our forefathers" -- always an expression for the apostles -- a 40-day period of Lenten preparation existed. However, the actual practices and duration of Lent were still not homogenous throughout the Church.
So, I suppose that the answer is that there is evidence that it was 3 days some places, but this was never official policy of the Church Universal.
As a note: the length of Lent is not a doctrine, but a practice. While it is EXTREMELY doubtful that the length will ever change, it is theoretically possible for the Vatican to make some pronouncement changing it.