These things do happen, fortunately not always with disastrous results!
You were lucky not to get burgled with the keys, you must live in a very safe place!
I once found a wide bolster, more or less new, under the bonnet of a Renault 17 I had just had a mobile welder working on, he was happy to have it back.
I have similarly found a 8 mm spanner inside a panel on a new Toyota, must have been there since manufacture.
But the funniest was after going to the National Kit Car show at Stoneleigh where we found ourselves helping each other with various repairs and adjustments going on, more than usual. I lent spanners etc to two members of my club and at the end of the weekend noticed I had one spanner too many and one too few. (Using a tool roll helps to keep track!). No one seemed to know what had happened, so I wrote a pastiche in Hercule Poirot style, in the monthly newsletter, to try and help sort it out. This was appreciated but, still nothing. But about 3 months later a Cobra owner looked up under the nearside front wheel arch and there was my spanner, still attached to a suspension bolt! Lord knows how it never fell off! Simialr to your clutch bleed spanner. I still have the extra spanner, and what is weird is that all my tools at the time were AF as all three cars worked on were based on old Brit vehicles, two, Jag and one Morris, or BL.
Wifey is now getting me the magnetic dish for my Valentine's Day present! Who says romance is dead!