Thanks, Ken. The uploader is not creating the element, $_POST["myuploader"].
It is, however, creating these elements in the $_POST array:
$_POST["UploadLib_Uploader_js"]
and
$_POST["AjaxUploaderFiles "]
Neither of those vars contain a filename. Nor do the other uploader vars in the example. (When echoed, they are empty).
The selected file is moved and saved OK but I am not able to figure out how to write the filename to a var for databasing.