Mr Rodge;
I bet you won't do it again! I admire your post there are plenty of pilots on this forum who believe they are steely eyed sky gods who couldn't make such a silly mistake, and some with thousands of hours who have logbooks and memories full of silly mistakes which they share in the cockpit or over a beer.
I've done the fuel cap thing, and in 14,000 hours lots of others as well, you might have dropped a clanger, the mistake would be not to learn from it.
Just make sure next time you fly you don't miss something else because you are focused on the fuel caps, I've done that one too..................