I have noticed the gun site disappear on my iPad3 but it only happens after jumping in the chute and actually shooting. Doesn't happen all the time, but the majority of the time.
Ok so step by step:
- You get shot down
- Choose the chute
- Fire at incoming planes
- Respawn with site missing
- Zoom out and back in to bring the site back.
Haven't really paid attention if it goes away if you get shot before you can shoot, if you have to land first or not, or if you hit a plane from your chute or not.