If you lose the physical parts of your licence, either paper or plastic you should apply to the dvla for a replacement.
If the DVLA have lost evidence of your licence entitlement you will need to pass a theory and practical test.
The loss can happen in a number of ways.
Your licence might be revoked by the courts and the wrong details entered on the DVLA system.
You may send your licence to the DVLA for updating and they may lose it or enter the wrong details.
Unless you can provide evidence of your test pass you will need to pass a new theory and practical test.
The only acceptable evidence to our knowledge is your original driving test marking sheet or pass certificate
If you do not have this evidence we can usually get you through a theory and driving test within a week of getting your provisional licence details.