iMessage notification dissapear

[Amandapaul]

My boyfriends iMessage notifications disappeared from his lock screen on his 6S plus without the phone being unlocked and is now accusing me of unlocking his phone and looking through it. Is there a button combination that would cause the notification to disappear or does the phone keep track of when it has been unlocked to prove I didn't touch it

 

[JamesMB]

My boyfriends iMessage notifications disappeared from his lock screen on his 6S plus without the phone being unlocked and is now accusing me of unlocking his phone and looking through it. Is there a button combination that would cause the notification to disappear or does the phone keep track of when it has been unlocked to prove I didn't touch it

What kind of notifications does he have set? Banners will disappear and Alerts require an action...

 

[Blujelly]

Is he viewing the iMessage on a different device, that is logged into the same Apple account?