Texts go missing on restart

I have an iPhone 4. I upgraded to IoS7, and now I find that, if the battery runs out and I restart the phone after plugging in the charger, most of my text messages have disappeared. I am left with a small and apparently random selection. All I can do to retrieve them is wipe the phone and restore it from an iCloud backup, which is a long and tedious process and anyway doesn't retrieve my most recent texts.

Is this an IoS7 bug, or is it just me?