I see threads all the time with locked up phones and people wanting to snoop but can't due to password changes/never knowing it etc. Do you know your DP's password? I know DH's and he knows mine. We don't snoop (to my knowledge) but I'm always able to get in if I wanted to, same for him. I thought this was normal?
Is it not the done thing? Do you know your partners passcode? I'd be very suspicious if he changed his without telling me/if I'd done the same he would be suspicious.