I have Gmail as well, and found a way to show my notes on my iPhone again without having to copy them back over manually.
Go to Settings > Mail, Contacts, Calendars > Gmail > turn on Notes
Go back to home screen and check your notes. They should be there (hopefully).
What had happened to me is this: I had accidentally turned on Notes in the Gmail settings and then turned them off again, so ios7 transported my notes into Gmail. But when I turned off Gmail notes, they disappeared from my phone. When I turned Gmail notes back on, my notes came back automatically.
So now my notes get updated in Gmail when I update them on my iPhone. Nice backup plan to have them connected to Gmail...
Hope this helps. Thanks.