should I say something?

So there's this guy I met recently and we talk everyday. Yesterday he was saying how he's super trustworthy and all this stuff. Then he texted me this morning and was all like sorry I fell asleep. Then in a group chat we're both in (he always talks to people in it I hardly ever do) he was talking to some girl and he knows I can see everything, and he says I was up at like 3:30 we should've house partied(it's an app) and now I'm just like wtf....: I mean I know it's stupid and normally I wouldn't saying anything but he's always saying how he's straight up and honest so it just seems like a red flag to me 
Edit****
Okay it has nothing to do with the other girl, let me make that clear. I don't care he can talk to whoever he wants because we are not together. But the fact that he told me he went to sleep and then told someone else (girl or not) that he was awake until 3:30 is where I have the problem. He didn't have to say anything to me, he could've just ignored the fact that he didn't want to respond instead of telling a white lie. That's the problem I have with this.