If you have lost or mislaid it you should contact the DVLA as soon as possible https://www.gov.uk/contact-the-dvla
If it has been sent to the police or a court for penalty points you must contact the police force or Court service who you sent it to and then contact the course provider to explain your situation. They should be able to assist.
Do NOT arrive at the course venue without your licence without first informing the course provider as they will probably refuse you access to the course and you may be asked to pay for another course, or your case may be sent back to the Police who may activate the Criminal Justice process
For more information on this matter click this link https://www.gov.uk/penalty-points-endorsements/Handing-over-your-driving-licence-for-endorsement
If not, consider contacting us.