Well the file is only in the tmp folder until the form handler script finished executing, then it is automaticly deleted, this is php's way of keeping things clean, what you have to do is have the php script that is recieving the data copy it to another directory before it disapears.
$newfile = $fileroot.$FILE_name;
$tempfile = stripcslashes($FILE);
$ret = @copy($tempfile, $newfile);
Where FILE was the name of the form item that was being uploaded. <input type="file" name="FILE">
stripcslashes() is used in the case of Win32 systems uploading files, they to double the backslashes for compatability reasons.
