Make Sure You Can Prove It !
Good point and remember that any competent FTO will always want official and original proof of qualifications and ratings before allowing anything to which you are, supposedly, entitled. Remember that emails, Faxes and photocopies probably won't be of any use.
This is a persistent and predictable problem when pilots/students want to go elsewhere and it seems that some delay or hold documentation so that you cannot move elsewhere.
However, aircraft owners, examiners, instructors and insurers are entitled to protection from liars and others who aren't able to produce the relevant docs.
Plenty of people who are perfectly 'genuine' have wasted a lot of time and money because of deficient paperwork so do heed these warnings.