If it was saved in 2010 format it should look the same on any version of Autocad. Your colleague should be able to open the converted drawing and see exactly what you're seeing. But, I don't know of any reason why this would be happening unless maybe he's not using plain Autocad? You need to find out exactly what program he's using or if he's using any third party add-ons.
Also, is your colleague positive that he moved the gate house surround into position, or did he copy it into position and maybe left the original in place and didn't delete it before sending you the file?
If you can post the drawing, we can take a look, but I don't know that we will be able to find anything wrong with the drawing.