HI there Sabastian Ranguis.
I too actually suffered this same type of fate WHEN I was running FCP 10.0.4, earlier this year. You might try what I tried and see if the timeline returns, which is might not.
1) Go to your Final Cuts Projects and Events Folders are located on your hard drive
2) Go into the Final Cuts Projects folder and look for the automatically saved backup of the project "currentproject." Look to see the file size there. If it says something like Zero or "0" bytes, well then, you are SOL. If it has a number in there, like 10 mb or whatever, then your timeline is probably there, but just not accessible through the Final Cut structure. Hopefully, you have a reasonable-sized number for that file.
3) IF there is a number there, go ahead and double click on the currentproject file and it will launch FCP 10.0.4. You'll likely get a window that comes up and gives you some warning that you have to open files from within FCP.
4) When the app launches, LOOK for the EVENTS folder that you were drawing from and see if its there. IF it is, click on it and if it loads, then it will also load the project with it and you will likely (maybe) see the project appear in the window; however, you still may not actually see a timeline. BUT, if the project appears in the FCP window - IF you can see its contents, that is a good sign.
5) On your FCP menu bar, look for WINDOW and make absolute certain to SHOW the TIMELINE INDEX, not HIDE it!
6) If the timeline shows up, your saved. IF it still shows a grey bar - NOTHING, then I don't know what else to tell you, but maybe someone else has a solution.
***The main thing is this: IF you can get that timeline to show up, then make a Command C on your keyboard. Make a NEW PROJECT and paste the your old timeline to the new project using Command V on the keyboard.
I've had other FCP "dissapearing acts" happen to me with various projects and I've tried all kinds of things to repair these problems. Some have worked and some have not. IF you can a timeline back...IF YOU CAN, even if it is filled with tons of those red "Missing Events" windows, you can always get most of the stuff back by doing a RELINK of the missing files. But, I've had cases where my timeline is actually still on my hard drive, but I just can't see it! in FCP. But, I have done those steps above myself and strangly, some stuff has come back! You are just going to have to experiment around and see what happens, without loosing your cool. Just stay focused and keep your presense of mind and try different things. That's the best I can tell you. The WORST CASE scenario is that you will have to RE-BUILD the whole thing! NO FUN! I know.
Now, one last thing: I went to www.digitalrebellion.com and purchased their VERSIONER program. This absolutely has saved my butt a number of times. It's a great little utility that they have available that WILL MAKE backups of your projects automatically and you can annotate them to know which backup is which. I recommend that every FCP editor obtain this little utility that they sell. So then, it doesn't matter what FCP has for a currentproject backup. You can always REVERT back to a previous saved version of it through this app and you will save yourself a lot of grief.
BTW, I DO NOT recommend that you UPGRADE to FCP 10.0.6. Read the forums! I have it and it is infested with BUGS! There are all kinds of issues with this version from Apple. They really screwed up a lot of stuff in the FCP platform. I'm continuing to use it...but very cautiously and I MAKE backups of EVERYTHING, daily. Apple NEEDS to get its act together and fix the issues with 10.0.6. Right now, you can expect a fair amount of grief, IF you upgrade. Yes, it has a lot of new, nifty features, but its still a headache.
Be well and stay cool.