I too have had this happen to some maple leafs that I was storing. I too had the rubber band on all four sides and guess what I had i nice toned x on the coin. For fun once that happened I dipped the coin, FYI it won't remove it all the way and leaves a lot of haze. Basically the coin is ruined so if anyone is storing numismatic pieces or bullion coins that you don;t want toned I would not in a million years use rubber bands. I learned the hard way, just happy it was bullion coins so my education was fairly inexpensive.
You could use nylon ribbon instead. If you really wanted to spend money, there are rubber bands made from silicone rather than rubber. They're made for cooking or other applications where there's heat involved. I've never heard of a coin turning from a rubber band through a flip while being sent for grading. That plastic is a lot thicker than the mylar on a 2x2.
In 2009 I got 4 rolls of one the cents that came out that year. They were in plastic rolls from Brinks. There was a rubber band around them. A few months later, when I got them out, there was the outline of the rubber bands.
Way back in the day I cut slivers of rubber bands to help the large cents for in my Dansco 7070 album. Months later, the rubber bands were stuck to the coin's rim and left black all over them. And that was old copper! Lesson learned.
