Warranty Exchange not accepted

I purchased a normal padlock from Chamberlain Centurion 1 week ago, which I used at my front gate. Within 3 days the lock failed, as it was rusted shut. I returned the lock, with the slip, to Chamberlains, but the exchange was denied due to the fact that I did not have the third key. <br> <br> The issue is that how can a product fail within this short period, and then the client need to motivate for exchange. Within three days refers to either a latent defect, or poor manufacturing practises, and the onus is now on the client to return at his cost and effort. I would really feel uncomfortable if I supp**** a product for security applications that failed in 3 days.<br> <br> <br> <br>