File Left Open in Excel 2010 but not in Excel 2013 but Why?

Question

   
Hi All,
After running the four lines of code below, if I try to open the 'MyFile.XLSX' in the windows Explorer I get a message saying  'File in use by 'another user'. However if I try to reference the file in Excel via VBA it is clearly not accessible (and
shouldn't be). So why after copying all worksheets to another workbook is it still ready only?
Is there a way of ensuring the file is writeable once again via VBA (since the object can not be referenced any longer?)
Thanks in advance of any enlightenment
Steve 
Dim pmWkBk as Workbook
Set pmWkBk = GetObject(Workbooks("MyFile.XLSX"))
pmWkBk.Sheets.Move After:=Workbooks("MyOtherFile.XLSX").Worksheets("Sheet1")
Set pmWkBk = Nothing
Steve Stretch

Answer 1

So, 'the original workbook no longer exists in the Excel object model'.  I don't think that's possible.
It is 100% possible because once all the sheets of a workbook have been MOVED to anther workbook the original workbook doest;t exist. try it yourself...code
below was recorded and the last line added.
Cheers
Sub Macro1()
' Macro1 Macro
    Workbooks.Open Filename:="C:\Users\Win7\Desktop\Hello.xlsx"
    Sheets("Hello").Select
    Sheets("Hello").Move Before:=Workbooks("Goodbye.xlsx").Sheets(1)
    'then the bit you say is impossible - this is where you would get a subscript out of range error
    Workbooks("Hello").Close
End Sub
Steve Stretch