Alas, Dan, I have a similar problem with shoes, keys, cat treats, earrings...invariably I find the missing offender where I first looked for it. Just read an article on why we can't see what is right in front of our faces. Lost it or I would copy you on it.
Now go back to wherer you found the first boot and try again.
See if my blue earrings are anywhere close by while you're at it.
Mary