Just want to know why ?

My husband has this friend that he used to work with. they used to talk pretty regularly and he never told me that they talked but he would Tell me about other random conversations he had with people from work throughout the day. I confronted him about it when I saw him texting her and he said they just like to talk about work. And if that's true why not just tell me?

it's been over a year they don't work together anymore abd they don't talk as much (that I know of) but they still communicate on Facebook. I happen to see her message pop up when he was showing me something on his phone. He ignored the notification and act like it never happened. I asked him why he never tells me they still talk and he said he just doesn't think it's that big of a deal.. But he has plenty of female friends so it's not like he thinks I would be mad he has a female friend.

so I did a bad thing and I went through his messages this morning when he left for work. I needed a confirmation that he was just being weird about it and there wasn't anything going on between them.

And I'm right there's nothing there. all the conversations are about work and stupid people they make fun of that used to work with them, memes and YouTube videos. No emojis no flirting just super casual conversation so I can't understand why he never brings her up. It bothers me a lot and he doesn't seem to understand. Lol why are men so weird ??

it just makes me wonder what they talk about on his phone and now I feel like I opened up a can of worms and I need to come clean to tell him I snooped through his things but that I'm also feeling concerned and having some trust issues about this.

What do I do?!

** it's not that I'm jealous or insecure he voluntarily brings up conversations throughout his day, not all day every single day but sometimes he'll come home from work and have a story to tell me and say "so and so texted me". he has never ever mentioned this girl once in our entire relationship yet they talk on a weekly basis. I feel like he should at least mention her if they're that good of friends

I don't expect him to tell me every conversation he has but he has never once told me about this person that's the point I'm getting at. I've only ever seen them talking because I happen to look over when he's on the couch next to me. I don't care that their conversations are innocent, At this point I don't care if they're flirting, I don't even care that it's a woman, I would feel the same if it was a guy. What I care about is why does he purposefully not mention this one person. if you're such good friends with someone (man or woman) You think you would tell your significant other eventually.