Text messages are all stored on the phone. However, your cell phone company does have records of your text messages and you can access these...providing you have a subpoena. Outside of that, there is no way to recover your lost messages. There are some 3rd party apps that can backup you text messages tho...SMS Backup is one example (thats safe as far as I know). Sorry about your loss.
I have a Pantech Impact that henceforth I have had no problem with. However last night it shut itself off and when I rebooted it had deleted all of my text messages and text message drafts. Is there any possible way to get the texts back? I'm looking for one in particular, as it contained something of important sentimental value to me.