Project has disappeared

I've spent the whole day editing a project and all day final cut pro x has been freezing. The only way I could unfreeze it is by forcing it to quit and unplugging my external hard drive which I'm working from (as there's not enough space on my mac) I couldn't eject it properly as it says it's busy with final cut so I just have to pull out the usb.

All day I've been unplugging the external hard drive (Seagate 3TB) and plugging it back in, shutting and reopening final cut pro. I was almost finished when I opened final cut pro again and to do the last bits of editing and then my project just seems to have vanished.

All of the media is still there but the project itself is nowhere to be seen. On the event there's a yellow triangle warning sign listed beneath the library. It's really irritating so I have 2 questions.

1. Is there any way that I can regain the project?

2. How can I stop this from happening in the future?

Have you checked your library backup?
Should be in /Users/[username]/Movies/Final Cut Pro Backups/[libraryname]

Suggestions, what I'd do.

1 - Use "Preference Manger" to delete FCPX's pref files (won't touch your work).
2- Run Disk Utility to "repair" (verify is useless) all connected drives (especially that USB you disconnected).

If needed, run "FCS Remover" to 100% remove all of FCPX's system files (won't touch your work) and reinstall.

Personally, I'd run Disk Utility and Disk Warrior on that USB drive before doing anything else. Back it up first if possible.

AND, as JasonP wisely said, go find one of the library backups. This will probably be necessary. But I would hope not.

Thanks but how do I delete the preferences? Where do I find that option?

Sorry I'm a bit of a newbie!