This does not scale well

Here is a piece of code I just found:

# new location
# creates new record or seeks empty record marked by group_id = -2
if($CGI_DATA['new'] == 'New Location') {
  # look for empty - abandoned record
  $SQL  = "SELECT * FROM location WHERE group_id = -2";
  $result = mysql_query($SQL);
  if($row = mysql_fetch_array($result)) {
    $CGI_DATA['location_id'] = $row['location_id'];
  } else {
    $SQL  = "INSERT INTO location SET group_id = '-2',location_bname='New Location',location_roomnum='',
    $result = mysql_query($SQL);
    $CGI_DATA['location_id'] = mysql_insert_id();

A little background: this application has a number of groups each of which can specify several locations. What the above code does is it inserts a location with an "invalid" (-2) group_id, and then allows you to "edit" that record on the next page load. I don't know how they thought this was acceptable.