Hello! The compass app cannot be deleted so maybe its been moved into a folder somehow, try searching the iPhone for it (pull down from top of the screen). If not try syncing with iTunes on computer
1. Locate the Compass app.
2. Tap and hold on the Compass app's icon until all of your icons begin to jiggle.
3. Drag the Compass app's icon to the desired home screen.
4. Press the home button.