So today I got the update from awhile ago, I booted up forza 6. I have collected almost 200 cars with 1,000,000 dollars in the bank. But then all of a sudden the starting trailer starts playing, and then the first race starts. I lost EVERYTHING and can’t find a solution and am very sad 
especially because I spent 115$ dollars on the version I have. If so can somebody help me find a solution? Does anybody have this problem?
Might be Cloud Synch problems. I had a similar issue when my Xbox Factory Reset itself. Try and synch to the Cloud again and make sure you select your file that contains all your work.
I had similar problem 2 weeks ago, refuse to put any more time into it if all progress can be lost at any moment. Have been in touch with Microsoft about it. They tried all they could and refereed me to Turn 10. So far all methods to even contact them have failed.