Faced the same problem. I was trying to restore it via deleted files restoring tools, but it failed. So, there is no other way: you should issue another application.
Of course, any other your application you can upload with other certificate. It is used only for the security purposes: to ensure that upgrading person is the one who is the author.
Generally, the only advise that exists on keystores: always backup it!
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
