This is a current limitation with Lotus Notes Traveler that we are working to get posted into the Info Center.  The issue with the Trash folder is that it is not a real folder in the mail file.  It is a view, like All Documents view and special handling would be required to handle it like a folder.  A requirement has been entered and will be investigated for future releases of Lotus Notes Traveler, but at this time it is not known when or if this function will be added.