Walk Behind Lawn Mowers

Hello I bought a 7021P Push Lawn Mower in August of 2011 from Amazon.com. Two weeks ago the left rear wheel cracked and fell off. According to my research, this is a warranty repairable item. So I took it to my nearest Husqvarna service center which is Billings in Royal Oak, MI. They told me that since I purchased on Amazon, they cannot help me. Please let me know how I can fix this problem. That's a very disappointing failure for a 1-year-old product. Especially since I have used the mower about 12 times so far with each session lasting roughly 20 minutes. See pictures below. Thank you.