I've had this happen to me three times since I started using this phone. The first two times, the phone said I needed to force close Messaging, and then when I opened it again, they were all gone. First time this happened I cried, since I lost a locked message from a friend I had a falling out with.
It did it again a couple of weeks ago, with no warning, but left 3 texts from the same person. I've heard this was a problem with some people, I'm just wondering if there's a fix to it. I'm tired of losing conversations!