I was at Best Buy yesterday looking at cases when this situation happened.
The "damage" was a tiny (smaller than pin head) nick on the back chamfered edge. My wife couldn't even see it.
The guy was basically throwing a temper tantrum. They wouldn't let him open anymore because they were promised to others. They told him he could return it, take it to apple, or wait.
He was demanding they open other people's phones for him. It was pretty amusing. He kept saying "my money" this, and "I deserve" that.
The manager came over and told him that he didn't deserve anything, and that he could take his business elsewhere. He was polite, and didn't take crap from this OCD nightmare.
The guy punched the rack of cases on the way out.
So no. Best buy will most likely not let you open other people's phones just for your hunt of perfection.