Hehe, I'm dense. Do you know how many times I had to read that, to put together your name...?
sigh
Sounds like my xh. I would have snooped, too. (Yeah, I know...) It think if, and that's a big if, it were me, and he didn't contact her anymore (verifiably), then I would just let it go. Otherwise, a strategic talk would be in order. He obviously knows something about it wasn't right, or why bother to hide it?
That leaves me with two scenarios. One: Your H realized he was being an idiot, and decided (voluntarily) he needed to back off. (Unlikely, but possible.) Two: He didn't realize it, and either is hiding deeper or she cut him off. (For whatever reason.) I suppose my advice would depend on which of these scenarios it is...which wouldn't be obvious for awhile, anyway...