Not expecting it would be fine if she didn't say to stop and and that she didn't want to have sex. Saying stop and that she doesn't want it, means she doesn't want it and that she is against it, and that's what makes it rape. Just because it wasn't violent or anything doesn't change that.
If she hadn't said to stop and that she didn't want it, if she had instead said she was happy that he surprised her then I wouldn't have any problem with it.
If the game going forward doesn't treat this as a rape scene, and if there are no similar rape scenes, fine. But please be more careful and clear in future.
What you intend is one thing, what you write and show in the game is another