Sad to hear your story. I left my Yahoo mail and used GMail instead due to Yahoo's policy of deactivating accounts that's never been opened for couple of months. But I do hope you could retrieve your account as you said that it's somehow valuable to you.
Maybe this links could help:
https://ph.answers.yahoo.com/question/index?qid=200801272005...
https://ph.help.yahoo.com/kb/yahoo-account/account-locked-sl...