to put something somewhere and then forget where you put it, so you cannot find it easily
I had misplaced my keys, but they were in my coat pocket.
She misplaced her passport before the trip.
Misplace usually suggests that you may find the thing later. Lose can also mean that it is gone for good.
Common phrases & grammar
misplace your keys · misplace your phone · misplace an important document
misplace + something
misplace + something + in/on + a place