My IP4S has been in an SGP Vintage case since the day I bought it, screen protector on the front but not the back. When I removed the case to take photos prior to selling it, I found what appears to be air bubbles near the edges on the back, five of them. Just what it might look like if there was a screen protector on, but there isn't. Has anyone heard of this before? Is it worth making the journey to an Apple store? I have tried to photograph this but it isn'y very clear. I have marked two of the "bubbles", the other marks are reflections.