What archived log is missing ? (ORA-38754 & ORA-38761)

SQL> FLASHBACK DATABASE TO RESTORE POINT BACKTOTHEFUTUR;
FLASHBACK DATABASE TO RESTORE POINT BACKTOTHEFUTUR
*
ERROR at line 1:
ORA-38754: FLASHBACK DATABASE not started; required redo log is not available
ORA-38761: redo log sequence 15 in thread 1, incarnation 26 could not be accessed

SELECT NAME 
  FROM V$ARCHIVED_LOG A, V$DATABASE_INCARNATION I 
 WHERE A.RESETLOGS_ID = I.RESETLOGS_ID
   AND A.SEQUENCE# = 15 
   AND A.THREAD# = 1
   AND I.INCARNATION# = 26;
   
NAME
--------
/DOCBROWN/oralog/archive/MARTY/arc1_15_743268414.arc