Are you missing something? Now the whole world will help you find your pet, keys, documents or anything you miss. I will tell you what works better than just putting up „HELP FIND!“ posters in your neighborhood.
Point out the approximate location where it could have happened, so that the users in this area will be on guard.
And if you're lucky - one of them will find what you are missing, and using an in-build messenger will write to you about it. A certain reward could motivate people to help you in your search - just indicate the amount of it.
What you miss may have already been found - just look around in our Lost&Found bulletin board.