thnx for your answers Jim
I am absolutely positive sure that i was the last one in the studio here. So nobody else could have saved my project. 
I made a screenshot from the corupted file data (not the Autosave file but the regular file with version 0.9). The making of the file was on 15:55 the altering (that is saving i guess) is on 20:09. I left the studio at 19:45. The last time i tried to open the corupted file is a day later on 19:52.
So i am wondering what alternation (i don't know the proper English word for it...) Premiere did on it's own, and if this can cause a corrupt file?