![](https://images.toofab.com/image/59/o/2010/05/27/59d2a08889de5cdb9a4db75651b8011b_md.jpg)
All eight American Idols from the previous seasons performed a tribute to Simon Cowell last night -- but David Cook was noticeably absent from the stellar lineup ... and now we know why.
A rep for David tells Access Hollywood the Season 7 winner was at a charity event in Kansas City.
Despite missing out, Cook twittered "Congrats to Lee DeWyze! So sorry I couldn't be there to see all my fellow idols. I'm there in spirit!"