I've gotten naialed up to 25-yards away from the backstop at my club's Indoor Range. I've even had blood drawn while shooting at the 7-yards line (about 10-yards from the backstop).
I'll echo what the ROs at your range said; this is why EVERYONE SHOULD ALWAYS WEAR EYE PROTECTION. Not much you can do.
Look at this video:
http://www.break.com/index/targetshot.html