AceShowbiz -

While many are thrilled by Kim Kardashian's engagement to Kris Humphries, one person is said to be left bitter. Life & Style claimed that Kim's ex-boyfriend, Reggie Bush, was left so upset by the news that he missed out the launch party for the Gumball Rally 3000 at the Playboy Club in London on Wednesday, May 25.

One eyewitness claimed to have overheard NFL player Cody Green, who happened to be Reggie's Gumball Rally 3000 teammate, telling a friend the reason why the 26-year-old backed out at the last minute. "We heard Kim got engaged, so we think that's why [Reggie] didn't turn up," so Cody reportedly said. "He must be pretty cut up. He sounded like he was, and that was why he didn't make it down."

Reggie and Kim began dating in late 2007. After several years of dating on and off, the two decided to end their romance for good in March 2010. Despite the separation, it was reported Kim made sure that Reggie knew about her May 18 engagement to Kris before the news was broken out to the public.

"Reggie was told about Kris and Kim's engagement this past weekend because Kim knew everyone would be contacting him for reaction," an insider told Hollywood Life. "He was apparently made aware of the People magazine cover as well."

Kim herself is currently celebrating her engagement with new fiance Kris and his family with a planned vacation in Monaco. About the trip, Kris told People Magazine, "I wanted to propose before the trip so we could really spend some quality time together with my family as a couple. I planned it out this way." Kim chimed in, "We're celebrating ... on a family vacation with them."