SegmentReader.loadDeletedDocs FileNotFoundExceptio load _hko_7.del - corrupted index [LUCENE-4467]

We're using lucene to index XML. We've had it in test on a server for some weeks with no problem, but today we've got the error below and the index seems no longer usable.

Could you please tell us

1) is there a way to recover the index?
2) is there a way to avoid this error?

I can supply the index if needed

many thanks

Tue Oct 09 17:41:02 CEST 2012:com.siap.WebServices.Utility.UtiIndexerLucene caught an exception: 32225010 java.io.FileNotFoundException
e.toString():java.io.FileNotFoundException: /usr/local/WS_DynPkg/logs/index/_hko_7.del (No such file or directory),
e.getMessage():/usr/local/WS_DynPkg/logs/index/_hko_7.del (No such file or directory)
java.io.RandomAccessFile.open(Native Method)
java.io.RandomAccessFile.<init>(RandomAccessFile.java:212)
org.apache.lucene.store.SimpleFSDirectory$SimpleFSIndexInput$Descriptor.<init>(SimpleFSDirectory.java:71)
org.apache.lucene.store.SimpleFSDirectory$SimpleFSIndexInput.<init>(SimpleFSDirectory.java:98)
org.apache.lucene.store.NIOFSDirectory$NIOFSIndexInput.<init>(NIOFSDirectory.java:92)
org.apache.lucene.store.NIOFSDirectory.openInput(NIOFSDirectory.java:79)
org.apache.lucene.store.FSDirectory.openInput(FSDirectory.java:345)
org.apache.lucene.util.BitVector.<init>(BitVector.java:266)
org.apache.lucene.index.SegmentReader.loadDeletedDocs(SegmentReader.java:160)
org.apache.lucene.index.SegmentReader.get(SegmentReader.java:120)
org.apache.lucene.index.IndexWriter$ReaderPool.get(IndexWriter.java:696)
org.apache.lucene.index.IndexWriter$ReaderPool.get(IndexWriter.java:671)
org.apache.lucene.index.BufferedDeletesStream.applyDeletes(BufferedDeletesStream.java:244)
org.apache.lucene.index.IndexWriter.doFlush(IndexWriter.java:3608)
org.apache.lucene.index.IndexWriter.flush(IndexWriter.java:3545)
org.apache.lucene.index.IndexWriter.closeInternal(IndexWriter.java:1852)
org.apache.lucene.index.IndexWriter.close(IndexWriter.java:1812)
org.apache.lucene.index.IndexWriter.close(IndexWriter.java:1776)
com.siap.WebServices.Utility.UtiIndexerLucene.delete(UtiIndexerLucene.java:143)
com.siap.WebServices.Utility.UtiIndexerLucene.indexFile(UtiIndexerLucene.java:221)

---
Migrated from [LUCENE-4467](https://issues.apache.org/jira/browse/LUCENE-4467) by B.Nicolotti, updated Jan 21 2013
Environment:
```
Currently using:
java -version
java version "1.5.0_13"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_13-b05)
Java HotSpot(TM) Client VM (build 1.5.0_13-b05, mixed mode, sharing)
Tomcat 5.5
lucene 3.6.0
```

Attachments: [index.zip](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4467/index.zip)

Start with the stack trace through org.apache.lucene.index.SegmentReader.loadDeletedDocs, BitVector, and IndexWriter, then inspect the attached index.zip and the Lucene 3.6.0 environment details. Determine whether the missing _hko_7.del file can be recovered and what operation caused it to disappear; done means documenting a reproducible cause and a verified recovery or prevention path.

Written by the indexing model from the issue text.