TDirectory::FindObjectAny

ROOT
1

Hi,
I want to find a histogram which I stored in a any sub directory of the Root tree or a (known) file. I thought the FindObjectAny() Method was the right thing, but this fails if the TDirectory does not belong to a writable TFile (see the following example):

  *******************************************
  *                                         *
  *        W E L C O M E  to  R O O T       *
  *                                         *
  *   Version   4.04/02      29 June 2005   *
  *                                         *
  *  You are welcome to visit our Web site  *
  *          http://root.cern.ch            *
  *                                         *
  *******************************************

FreeType Engine v2.1.3 used to render TrueType fonts.
Compiled for linux with thread support.

CINT/ROOT C/C++ Interpreter version 5.15.169, Mar 14 2005
Type ? for help. Commands must be C++ statements.
Enclose multiple statements between { }.
root [0] gROOT->cd()
(Bool_t)1
root [1] gROOT->mkdir("test")
(class TDirectory*)0x9077a30
root [2] test->cd()
(Bool_t)1
root [3] new TH1F("testHist", "a test histo",10,0,10)
(class TH1F*)0x908ee68
root [4] gROOT->cd()
(Bool_t)1
root [5] gDirectory->FindObjectAny("testHist")
(const class TObject*)0x0

In the current directory FindObjectAny works:

root [6] gDirectory->cd("test")
(Bool_t)1
root [7] gDirectory->FindObjectAny("testHist")
(const class TObject*)0x908ee68

How can I search directory structures for objets?
Cheers,
J.