@op, if you want to know if flights are still good. just go to ba and check, if they are still good now they should stay fine unless they are for after the date on bottom of letter they sent you. To get your account back the only way to do it is by mail. Explain who it was for etc... The only thing is that if someone who flew on your account flew on another account they will not believe your letter, since they can see that one of the accounts were sold.
Good Luck.