This has been happening to hundreds of people since the phone was released. See Issue 5669 - android - Droid deleting all Messaging/SMS conversation threads at random or triple sending - Project Hosting on Google Code for details of people repeatedly losing all text msgs, posts since Dec 2009.
Bad news: posts since Dec 2009, no reaction from Google or anyone. I guess you're SOL if you lost text msgs.
Good news: folks at that site have been posting bug reports that Google would supposedly use to find and fix the problem. We've done our own homework, looks like the SQLite packaged with the Android operating system has a bug that corrupts your msg database and you lose it all. The good news is (according to the Android developer site), a new version of SQLite will be used in Android 2.2, which might fix the problem (if that's the only problem). Go to the above site, jump to the end and back up to post 424. Download the LostSMS.Txt bug report, open and search for the word corrupt. Be amazed as you read where the Android OS decides the database is corrupt and so must be removed.
Hopefully Android 2.2 will have the new SQLite, and hopefully that's the only bug.
Good Luck all!!! (P.S. so, um, why didn't Google find this, or at least acknowledge they had found it and would release Android 2.2 to fix it???)
Oh, and according to my verizon cell phone, it's June 9, 11:56pm East Coast (Virginia) time. I wonder how many minutes will elapse before Google deletes this (rather than have to admit this has gone on for over 6 months with out any acknowledgement of the problem. Heck, go to a Verizon store, ask them if they have heard of this problem. They will lie their arse off - "Oh no, the Droids don't have any kind of problem with text msgs being deleted." I've asked multiple Verizon employees in multiple stores. They all said the same thing......)