MacBook Pro :: Can't Boot To OS X Lion Partition

Recently my OS X Lion Partition disappeared. I have a late 2008 Macbook Pro. It's partitioned with Lion (10.7.4) and Windows 7. A few days ago when I started up, it booted up to the Recovery partition. I didn't know what was going on at the time. So I booted again w/ option key and it only gave the Windows and Recovery partitions as the options. After searching for a solution, I found a blog that said I can set up Lion on a external drive and I did that. I booted from the external drive and saw my "missing" partition in the Finders window. I clicked on it and it had folders and they were not accessible, in other words it was damaged. I tried to repair using disc utility and it couldn't be repaired. I installed DiskWarrior on the external drive (w/Lion) and I was able to repair the bad partition. I can now see all my folders and files. I tried verifying it in Disk Utility and it says it's fine now. I can access it from my Finders window as if it is normail again. Thing is, I can boot into it. If I press the option key at startup, it doesn't appear. I also can't select it as a startup disk as it doesn't show. I've tried searching but to no avail. Does anyone know what I can do so I can boot from this partition. I'm trying to get this to work so I don't have to reinstall and start over. My time machine back up is too old too (my bad).