"RECORD OF PRIVATE MESSAGES SENT"

There needs to be a section where a "Record of Private Messages Sent" can be maintained. If a person sends a detailed or lengthy PM and it is not received or the sender wants to reference the contents at a later time He/She cannot. This would save us a lot of time when it comes to responding to other questions on the site. Why has this not already been done? What can be done to facilitate this request?