First off your GSS is very out of date, you need to run the live update until your on 2.5.1.2266.
Second I would suggest running the remote install again and then see if they show up.
The main reason this happens to us is because GSS uses the mac address to identify PC's. So if we remove a PC, change the PC name and move it to another location, it still shows up under the old name until a refresh is done.
So I suggest running a config refresh on the entire folder and have them update then look around for the missing PC's.