When I purchased acid it was out in room temperature conditions for about 20 minutes. I then took that acid 3-4 weeks later and it did not produce any effects. Could it have evaporated during those 20 minutes in room temperature before it was put into a freezer?
.....no. Freezing is a good idea, and the stuff doesn't last forever. But it's not like that. I would tend to think you got bunk.