What a sad first post for you to be making. Cremation of pets is the same where I am. It's joint with other pets unless you pay for special time for just your own pet. We did the same thing for a cat who died in winter and could not be buried, as is our usual course.
I agree with the others that you are entitled to a complete refund. You did receive the urn and pawprint but this is a business that involves tremendous emotion and I can't imagine a business not making the overture and refunding everything.
Could you place a collar or well loved toy or blanket in the urn and bury that? To give you some closure? Your pup will live forever in your heart and memory and it would be a shame to let this sad incident cloud those special memories. I like the tree or special shrub idea too. Our yard has a special spot at the back. We can never move.