[Users] passwords deleted after downgrade ?

[mi]

Hello,

In a long due attempt to recover my forgotten passwords from the mail app, i finally found time to install claws-mails debugging symbols, but i had to downgrade from 3.14.1 to 3.11.1 all installed claws-mail packages (like pgp and mime plugins). 
After a fresh launch, all passwords of all accounts seem to be deleted (empty)!
( *sigh* that was a quite funny recover attempt, because now im in really big trouble.)
I
 just wonder, why this happen, and at least, why no warning ??