My family have various people to ask. I always ask Walter, who was a distant relation by marriage of ours and haunts his old home, where my parents now live!
On Thursday I needed my copy of the 'Malleus Maleficarum' and after turning my bedroom upside down admitted defeat and asked out loud, 'Walter, can I have my book, please?'- and there it was, spine-up, down the side of my bed, right in front of my eyes. I did of course thank him.
The Viz 'Top Tips' page suggests tying all your possessions to a long, long piece of string, and when you lose something, feeling along it until you find it again.
Works for me.