midnight club LA plz help!

hey guys basicly i was cruising around with the unlimited nitrous cheat on which stops you from progressing in career and i forgot it was on when i went to meet Booke about some racers downtown. He told me to go and find some one but after i realised i had my cheat on and turned it off, my mission log still had the "find booke" mission after i'd found him and the cutscene had played and now he has disapeared off the map so its impossible to find him! Any advice? It autosaved so theres no going back:(

Thanks guys!

almost same problem, i didnt have any cheats on. i have 33500 or more exp(idol rank) but it wont let me complete classic italian! ive beat karol 7 times , which is 14 races and its still in my active missions.