LOB Segment is listed in DBA_SEGMENTS, but has not corresponding row in DBA_LOBS
One possible reason is setting a LOB column unusable:

SQL&gt; create table t1 (c1 number, c2 clob);

Table created.

SQL&gt; insert into t1 values (1, 'A');

1 row created.

SQL&gt; commit;

Commit complete.

SQL&gt; select segment_name from dba_lobs where table_name = 'T1' and column_name = 'C2';

SEGMENT_NAME
------------------------------
SYS_LOB0000015673C00002$$

SQL&gt; select segment_name from dba_segments where segment_name = 'SYS_LOB0000015673C00002$$';

SEGMENT_NAME
--------------------------------------------------------------------------------
SYS_LOB0000015673C00002$$

SQL&gt; alter table t1 set unused column c2;

Table altered.

SQL&gt; select  table_name, column_name from dba_lobs where segment_name = 'SYS_LOB0000015673C00002$$';

no rows selected

SQL&gt; select segment_name from dba_segments where segment_name = 'SYS_LOB0000015673C00002$$';

SEGMENT_NAME
--------------------------------------------------------------------------------
SYS_LOB0000015673C00002$$


To find the table the orphaned LOB column belongs to:

select u.name, o.name TABLENAME, decode(bitand(c.property, 1), 1, ac.name, c.name) as column_name
from sys.obj$ o, sys.col$ c, sys.attrcol$ ac,sys.lob$ l,sys.obj$ lo,sys.obj$ io,
sys.user$ u,sys.ts$ ts
where o.owner# = u.user#
and o.obj# = c.obj#
and c.obj# = l.obj# and c.intcol# = l.intcol#
and l.lobj# = lo.obj# and l.ind# = io.obj# and l.ts# = ts.ts# and c.obj# =
ac.obj#(+)
and c.intcol# = ac.intcol#(+) and lo.name ='SYS_LOB0000015673C00002$$';

NAME                           TABLENAME                      COLUMN_NAME
------------------------------ ------------------------------ --------------------------------
BP                             T1                             SYS_C00002_16120712:10:58$


To remove the column and LOB segment:

SQL&gt; alter table t1 drop unused columns;

Table altered.

SQL&gt; select segment_name from dba_segments where segment_name = 'SYS_LOB0000015673C00002$$';

no rows selected


Based on: Orphaned Lobs after marking LOB column unused (Doc ID 461651.1)