Just from my own (unverified) experience...
Sometimes LE tells searchers to be on the lookout for specific items. This tends to be true when the victim is thought to have wandered away on their own (such as someone with Alzheimers).
Just as often, though, LE doesn't say a word.
If you think about it, searchers are quite often not just looking for things associated with the victim, they are also looking for anything that might be associated with the perp.
If you tell people to be on the lookout for certain items, you greatly decrease the chances they will notice any item that was not specified.