Missing text messages-help please iPhone 3G

My 3GS iPhone powered off as the battery ran out, and after I recharged it, all of my text messages were missing. I can receive new ones, but all the old ones are gone. I tried powering off and on the phone a few times, but it did not help. I know that I can go to iTunes to restore the ones from when I backed-up last, but that was a few weeks ago. If I do that, I will still be missing three weeks of messages. Is there any other way I can retrieve these messages?
Is this common? All my contacts are still there and everything else seems normal - just all the text messages are gone.
Help please!
Thanks.
Toshiba