Get a dirty sock, old hanky, or pair of clean or dirty undies, tie
them/it in a knot, and yell:
Gremlin of snot!
Your balls in a knot
And so ye shall rot
'til my ____ I've got!
And then just sit back and relax; it'll come to you soon.
Or just sit down and read a book in the room where you are sure the
item is at, and just forget about it until some spot on your head
feels warm, then go looking in that direction - for example, if the
back of your head feels warm, look for your stuff behind you.