Out of the million safe ways to say the negotiation is not over, quite a lot are so obscure that most employees would not even pick up on the subleties. (And if we're honest, we all know coworkers who wouldn't get that hint even if the manager outright told them their hands were tied at this point in the negotiation)
There are a million legal/safe ways to say that the negotiation is not over just keep pushing.
It could also hint that the manager thought the commenter was one of those social cripples that cannot handle negotiations professionally but it doesn't sound to be the case.