Oracle Database Discussions

Hi Experts,

Need your help to understand a basic tablespace clause while creating any object .
I have a table owned by user A and reside on tablspace tb, table A has two indexes i1 and i2 , i1 index owned by user A and mistakenly created index i2 owned by user B .
index i1 resides on tablespace tb_index , mistakenly created index i2 also resides on same tablespace tb_index .
I have a question on above given scenario

Index i2 that got created by mistake resides on tablespace tb_index , despites of mentioning any tablespace clause . How it can be created on tablespace tb_index when developer didnt mention the tablespace .
tablespace tb_index is neither default database tablspace not default tablespace for user B .

Any clue on this will help me alot .

Thank you