LOL..Nan, it doesn't work with everyone. They have to come looking for you...you may be under the bed for a long time if the person you wait for gets side-tracked by something.
Right after sending my son to his room for some transgression, we looked for him and he wasn't in bed...he was about 5 or 6..we scoured the neighborhood for him..talked to his friends and were on the verge of calling the police (can you imagine how terrified I was?).
Where was he?
Under his bed asleep.
He crawled under there because he was mad at one of us...and fell asleep...
I was so relieved to find him that I forgot why he had been sent to his room!
British Columbia, Canada