why? If you hold an ATPL you are covered for CPL but not the other way. If you "lost" your ATPL through medical or being pulled for some sin then you lose everything. Medical loss could mean could possibly get a Class II or an NPPL and continue flying privately.
If you were applying for a job as at a charter company you would stand a much better chance than a candidate with a CPL if you held an ATPL. By ATPL I mean a real ATPL not an imaginary "frozen" one.
If you lost the paperwork you send in a form to the CAA and get a copy.
I can't see the point of the question!