Oh no! We can restore any lost level to you. In order to do this you can email us at Support through the Welder App by pressing the ? at the bottom of the menu screen and then clicking Contact Support.
Please make sure to reference what level you were on in your email.
As a safety net during regular game play you can save your game to iCloud by tapping the iCloud button in the game menu. Then you can load the game again and the game will be redundantly saved on iCloud.