Then I'll repeat my advice to you: you have to talk to him about it.

[She tips her head at him. There really isn't anything judgmental in her tone; it would be hypocritical for her to be. But nor is there any softness in her gaze, because he doesn't need softness right now.]

Corner him. It doesn't matter if he wants to pretend nothing happened; something did, and I promise you he hasn't forgotten it either, if only because he won't speak of it. And if at the end, you both decide it was a one-time thing, you'll at least have the confirmation and can move forward from there.