The bonus was announced earlier in the year at E3, but was mysteriously absent from retail copies of the game. EA said that it was offering PlayStation 3 players a window of exclusivity on all Battlefield 3's DLC instead. This didn't sit well with fans.
Thankfully the publisher's taken steps to correct the problem, announcing that starting this weekend it will offer free copies of Battlefield 1943 to players that have redeemed their Online Pass for Battlefield 3. Europe will receive their copy this weekend, with North America following on December 10th and Japan on December 17th.
If you need instructions, EA's set up a help page for the issue. All's well that ends well?