If that index tablespace realy contained only indexes, then simply runing the "indexfile" created with "IMP INDEXFILE=..." will not be very helpfull.

All those indexes that should be created by the indexfile are probably allready created in the database! During the first import imp executed all those CREATE INDEX commands. As it couldn't find the index tablespace, it created those indexes in the user's default tablespace. Only if there were space or quota problems in user's default tablespace those indexes weren't created. In this case check the imp log file for any errors regarding CREATE INDEX commands.

If those indexes are allready created, you can simply move them to the index tablespace by using ALTER INDEX REBUILD commands.