Consider

use strict;
use warnings;
my $tree = {
    'Stuff1' => 'Data Stuff',
    'ImportantStuff' => {
      'MoreStuff' => {

      },
      'VeryImportantStuff' => {
         'Item1' => {
            'Description' => 'Need To Know',
            'Date' => '20040101',
         },
         'Item2' => {

         },
         'Item3' => {

         },
      },
   },
};

warn $tree->{ImportantStuff}{VeryImportantStuff}{Item1}{Description},$
+/;
die $tree->{ImportantStuff}->{VeryImportantStuff}->{Item1}->{Descripti
+on},$/;
__END__
Need To Know
Need To Know
[download]

If $tree is getting modified, it's not in the code you've shown. If the "data was not retrieved" maybe it isn't there (whatever your problem is, it's in your code, not what you've chosen to show here).