I personally dont think that there is anything we can do, you see the account holder of the clan must assign a new clan leader him/her self. We can't just change the clan leader as if your old leader does return then it will cause havok.
Is there no way to contact your old boss? Skype, TS, Email?
I will forward this thread to my Board Admin for his perusal and he will be able to provide you with a clear answer.