Rendered HTML has no ID associated with the dialog buttons

Rendered HTML has no ID associated with the dialog buttons

This is the JS displays a standard 'OK' dialog using jQueryUI:

function genericPopupDialog(dialogTitle, dialogBody, closeButtonText, dialogWidth, parentContainer) {

  parentContainer = parentContainer || "#bodyDiv";

  $("" + parentContainer + "").append($("<div id='genericPopupDialog'>" + dialogBody + "</div>"));
  $("#genericPopupDialog").dialog({
    autoResize: true,
    autoOpen: true,
    width: parseInt(dialogWidth),
    maxHeight: 500,
    title: dialogTitle,
    modal: true,
    closeOnEscape: true,
    buttons: [{
      id: "btnCancel",
      text: closeButtonText,
      click: function () {
        $(this).dialog("close");
      }
    }],
    open: function () {
      $(this).scrollTop(0); 
    },
    close: function() {
      $(this).remove();
    },
    dialogClass: 'center-dialog-buttons'
  });
}

And this calls that function:

function showStandardDialog() {
  genericPopupDialog(
    'Standard popup dialog example',
    'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
    'Close',
    '500'
  ); 
}

When I view the source code in a small test harness web app, I'm seeing the ID of the button which closes the dialog; btnCancel. However, when I incorporate this in a much larger web application, the button ID is not present in the rendered page, making automated testing a bit tricky. Both web apps are using jQuery UI v1.11.4 & jQuery v1.10.2. I'm fairly new to this aspect of JS, so any help would be greatly appreciated!