Once Oracle writes to a datafile deleting that file becomes very difficult. Looks like you've created a LOB dbf in the wrong directory. It would probably be best to move the datafile rather than blowing it away. Check out this:
https://docs.oracle.com/cd/B28359_01/server.111/b28310/dfiles005.htm#ADMIN11430
Also, with Oracle 12c you can leverage the cool feature of moving the datafile while online! You could use a simple statement:
See: https://oracle-base.com/articles/misc/renaming-or-moving-oracle-files
and look under "Datafiles":
Oracle 12c includes the ALTER DATABASE MOVE DATAFILE command, which performs an online move of a datafile.
SQL> ALTER DATABASE MOVE DATAFILE '/u01/app/oracle/oradata/cdb1/system01.dbf' TO '/tmp/system01.dbf';
HTH
Mark