It may be that it was just to early to see anything on the scan, I think that they dont even implant until day 20, I know that they are free floating until about day 15-18 so dont give up hope. The antibiotics should provide her with cover against most things that could have been brewing, the fact that she doesnt have a temp is good as it is the bodies natural defence to infection, which would seem to indicate that there is none present.
I know that I have seen a previous similar post, I hope that the poster sees this and pops on to answer!
Fingers crossed that everything is ok.
Mod edit: link to similar thread :
http://www.champdogsforum.co.uk/board/topic/114083.html