Major league rules grant rookie status to players with "not more than 130 at bats or 50 innings pitched in the major leagues during a previous season or seasons, nor more than 45 days on a major league roster during the 25-player limit (excluding time in military service, or on the disabled list)." Trout had just 123 at-bats with the Angels in 2011, but he appeared to have enough service time to disqualify him from rookie status with 56 days prior to September 1
Was selected to Major League roster on July 8, 2011.
Received an optional assignment on August 1, 2011; thus, was on the 25-man roster for 25 days from July 8th-July 31st.
Was recalled on August 19, 2011; thus, was on the 25-man roster for 13 days from August 19th-August 31st.
Thus, Trout was on the 25-man roster for 38 days in 2011.
Since Trout was on option for less than 20 days before being recalled again, he is retroactively credited with the days while he was on option.
Even though he now gets credit for those days, the fact remains that he was an active player on the 25-man roster for just 38 days in 2011.
Since he was under 45 active days on the active 25-man roster in 2011, he keeps his rookie status for the 2012 season.