One of the reasons we insist on having the cake back is because we want the physical proof of the cake. In our world, you can have your cake or your money, not both. Another reason is like I said above, we want to see you lie to our face. A third reason is if the cake is wrong (taste, texture, design) we need to know it for future reference so we can prevent it from happening. As I said, I'm not the full time baker now but she and I want to be able to assess the remaining cake.
It's not worth the time right now to contact the CC company premptively. However, if we are notified that there is a charge back, we have documentation to prove our case.
I also have some other tricks up my sleeve
We'll see if she comes in.
You'd be surprised at what people will bring back. We had one mom who spent $XXXX on a dress cake for her daughter and they didn't even eat it. Apparently the nanny who picked it up didn't secure it in the car properly and it had fallen apart by the time they got it home. They brought the whole thing back to us that Monday.