OP here w/ a happy ending and apologies to FedEx for besmirching their reputation. I called them at noon which is when the last rep said things should be investigated by. Their automated system seems to have a learning capacity. Previously when it told me the package was delivered yesterday and I replied B@#$S*&^, it would say courteously that it was confused and try even harder to help and shield the reps from me.
Today when I muttered that B@#$S*&^ in response to it again telling me it was delivered yesterday, it got me immediately to a rep who got me to someone who got me to what sounds like a local rep, most likely a manager.
He very calmly suggested that I might want to look in the mail slot, that perhaps it had fallen outside on the floor. I had already looked there but in case it had been delivered today, I thought I should look again.
I didn't see it, then decided to open the garage door to get more light to be sure. I didn't originally see it but when I was closing the door, there it was.
There is a small gap between the garage door and the mail enclosure---perhaps
1/32" or so.........took 2 thickness of a small postcard to fill so it hopefully won't happen again. Somehow the Fedex package dropped vertically down the slot and got wedged in that some gap. If it had remained vertical, I think I would have seen the reflection from the white surface even in the dim light. However after wedging in the gap, the envelope bent over so the reflections were not visible.
I couldn't repeat it and I doubt the FedEx guy could either. Anyway happy ending and my faith in mankind is restored. Now I can get gas at Costco again. Somehow the magnetic strip on the credit card has black markings which none of my other cards have. I think the Costco gas pumps are the only ones that use that anymore. Everything else uses the e-chip. How my card got those black marks is a mystery to me.