I did something like that once, too. Ir was time to complete an annual ignition tune up on the II-A and ordered the parts required from RN. I went through the box and started the job. Just as I"m almost through I realize there is a part missing.
I summoned up my best "stern lecture voice' and called; since it was after 3 pm, I knew the part would be a couple of extra days arriving. I let it be clear, with firmness, that as the Editor of the Rovers North News, this sort of thing should just not happen. After all, it even said on the packing slip that the missing piece had been shipped.
Eric handled it all with aplomb and stated he would research the problem and get right back to me with information. Meanwhile, I set to emptying out the box of all the shredded paper packing and - oops - there was the missing part.
Meanwhile, Eric called me back to apologize for the potential error, but also to note that the shipping crew even remembered the order and suggested that I should look carefully through the box.
"Ahem..." I stammered, I had already and I had found the part. Ever want to take back a phone call?