How can I get a record of a purchase of a LaCie External HD I purchased from the Apple Store

How can I get a record of a purchase of a LaCie External HD I purchased from the Apple Store

The Southlake Texas store, it was a few years ago.
I believe that it was less then 3 years ago and need to prove that.
I emailed LaCie for a repair and they told me that the warranty was up.
I believe that that is not true.
Obviously I cannot find my receipt.
They would not even explain how to send it back to them