A few months ago, my selling ID found herself in a similar situation. I'll switch to first person for the story . . . .
One buyer bought two things that I had listed. In my haste and happiness to have sold Two Things !!, I bought postage/label for the first item. Moments later, I realized that, duh, the same gentleman, at the same address, using the same eBay ID, had bought both of those things. I wanted to save him some money. I found a box suitable to hold both things, weighed and measured it, and bought postage/label for that box which held contained both things.
As I recall, I did send him a message that he should disregard the tracking number ending in, say, 1234, because the tracking number ending in, say, 7890, was for the package that contained both items. I thought all was well, until some days later I was notified of an Item Not Received case against me !! No, no, that can't be possible!
I contacted that buyer and explained it all over again. He told me that, when he filed the INR, he had not yet even opened the box I had sent him. (--whut?--) He was just trying to match up tracking numbers to all the things he had recently purchased. But once he opened the box and saw the Two Things safe and secure, he withdrew the INR case.
I was very glad he was honest, because he could have tried to cheat me out of what was in my mind a good chunk of money. I still try to save money for my buyers who buy more than one thing, and I am much more careful now about purchasing and printing postage until the packages are sealed.
