I had an interesting occurrence yesterday - a customer ordered x2 (physical CD) audiobooks, which was good

BTW, I purchased this site 2 months ago, and am still finding my way around the many traps for beginners.
1. How did the customer find that title on my site? Is there a link to another inventory somewhare else, or perhaps it IS in my catalog but I just can't find it? How did Google manage to index it?
2. Is it possible to integrate my AC site with Amazon (I am an affiliate, and was before I bought this site), so that if someone searches for a title, and I don't have it but it is available on Amazon, then they can purchase directly through Amazon? Amazon would get paid for fulfillment and shipping, and I would receive my affiliate commission.
I have search several likely forums on this second topic, but can only find old posts about what a good idea this would be.
Thanks for any ideas and help
Stephen