The thing you search for longest may have been placed carefully rather than carelessly.

The hardest things to find are rarely the ones dropped in a hurry. They are the ones a past version of you put somewhere deliberately, in a safe place chosen for reasons that made sense that day and have since gone. Habit finds carelessly placed things easily, because habit knows where you usually drop them. It is completely defeated by care.

When a search is going badly, stop retracing your steps and ask where a careful person would have put it. Think about what you were worried about at the time. And when you next put something somewhere clever, tell one other person.