Well, assuming the phone is gone and has zero chance of recovery... I would pickup/borrow a cheapo Windows Phone like an HTC 8S, Lumia 520 and sign into my MS account there. Assuming nobody monkeyed with the lost devices settings, by default, it should sync your backed up text messages to the new phone.
If you are still looking to obtain the phone, log into windowsphone.com which has some tools you can use such as ring, location...