The specified key is not present within this container error

Hey all! So I'm running the following code to essentially identify and extract an image within a database of images and assign it as 'rec'. Here's the code:

classdef (Abstract) db
  
  properties (GetAccess = public, SetAccess = protected)
    path; % path(s) containing the images and metadata

    info; % info for each image in the database
  end
  
  properties (Dependent)
    keys;
    imgs;
  end
  
  methods    
    function v = get.keys(db)
      v = db.info.keys();
    end
    
    function v = get.imgs(db)
      v = db.info.values();
    end
  end
    
  methods
    function db = db(varargin) % constructor
      % create empty database
      db.path = {};
      db.info = containers.Map('KeyType','char','ValueType','any');

      if nargin < 1
        return
      end

      % varargin contains one or more paths to add
      for ii = 1:nargin
        db = db.add(varargin{ii});
      end
    end
  end % methods
    
  methods (Abstract)
    db = add(db,pth); % add images in pth to the database
    
    img = getImg(db,key,varargin); % retrieve an image (by key) from disk
  end
  
end

I call the above script using this command

 db = imgdb.geisler('C:\toolbox\image-db\Set1_campus');
 

But when I try to assign an image with the specific key i.e the image file name through this

rec = db.info('D7H_3900')   

I get this error

Error using containers.Map/subsref
The specified key is not present in this container.

Can someone kindly point me towards where I'm going wrong? Note that to parse through each file, I'm using the rdir() recursive directory listing extension. So I'm thinking there might be a problem with that maybe? Thanks in advance!