I had a bag that had oats in it get moths. They were actually in the bag from the start. And I kept mine in a garbage can as well.
There’s not much you can do about it, besides report it to the company you bought it from and the manufacturer. I would also take it back to the feed store you bought it from.
If you report it to the manufacturer, make sure you get the serial number/lot number on the bag. This way they can see if they’ve had any other reports. Most companies are very happy and thankful when they are told about something wrong with their grain, because so many people don’t say anything.
"Take the time it takes, so that it takes less time."
"Expect a lot, accept a little, reward often."