You query dba_tablespaces and ts$ and the tablespaces are there. SOLUTION DESCRIPTION
=======================
The ts# column of the ts$ tables must be in sequencial order. When the sequence is broken all tablespaces above the break number are not accessible. Creating a new tablespace with occupy the broken sequence number if only one number is missing in the sequence. If more than one number is missing in the sequence then you will have to create as many tablespaces as numbers missing