How to check the SMS number when the mobile phone is not turned on?

If you can't find it, you can't find it in the mobile business hall. They said that in the SMS settings, it is useless to set the message validity to the longest time, which is just to set the time when the information you receive is stored in your mobile phone. It seems that the average text message is sent by the other party 24 hours a day. You can't get it if you don't turn it on, and it can't be redeemed.