Unexpected results using _INetGetSource

[charon]

Why is it that I can open the link I have to the expected webpage using _IECreate but when I try and download the source using the same link It downloads the login page instead even though I am already logged into the site with IE?   Does InetGetSource work with links that have variables in the link?

$BACCMAC = GUICtrlRead($MAC_input)  ;MAC address input

                $BACC_URL = "https://npgsui-external.test.net/bacc/jsp/bacc_mta_search.do?action=OPEN_DEV_DETAILS&mac_addr=1%2C6%2C6x%3Aee%3A96%3Ad8%3Aa0%3A60&page_number=0&searchType=MTA_MAC_SEARCH&searchQuey=" & $BACCMAC
                ;msgbox(0, "", $BACC_URL)
                $BACC_Source = _INetGetSource($BACC_URL) ;why is it downloading the login page when I am already logged in using IE and page opens without prompting for login

                ;write source file to disk
                $file = FileOpen("BACC_DATA.html", 2) ; The value of 2 overwrites the file if it already exists
                FileWrite($file, $BACC_Source)
                FileClose($file)

                Local $BACCArray = 0   ;holds web page with switch
                If Not _FileReadToArray(@ScriptDir & "\BACC_DATA.html", $BACCArray) Then
                    MsgBox($MB_SYSTEMMODAL, "", "There was an error reading the file. @error: " & @error) ; An error occurred reading the current script file.
                EndIf

                _ArrayDisplay($BACCArray)
                Local $IP_Results = _ArraySearch($BACCArray, ">IP", 0, 0, 0, 1)   ;return array index where IP was found
                MsgBox($MB_SYSTEMMODAL, "test", "IP Address: " & $BACCArray[$IP_Results + 3])

                Local $oIE_Signin = _IECreate($BACC_URL, 0, 1, 0)    ;attach=1, visible=1, wait for page to load=1   ;works: displays correct webpage
                If @error Then
                    MsgBox($MB_SYSTEMMODAL, "", "Err-oarrrr")
                EndIf

[Trong]

$file = FileOpen("BACC_DATA.html", 2+8+128)