The Premier League new-boys had agreed a £250,000 transfer fee to sign Situ from Lens, as well as a loan deal for Fulham defender Halliche, on transfer deadline day.
Rodgers said: "It's incredible really. When you have the Premier League, the FA, the French Federation, everyone sees there is innocence if there was maybe something that did not go through.
"But FIFA are saying it is not valid at this point, but until we get written evidence we will have to wait and see. But if that is to be the case then it is obviously very disappointing."