Completely by accident... DP was in the bathroom getting ready for bed, he'd left his phone in the bedroom with the radio on. A song came on that I really hate by Ellie Goulding so I opened his phone to switch stations, and it opened on a whatsapp chat he was having with my best friend, where he'd sent her photos of the engagement ring he's just bought.
I feel so bad that I know this! And to make matters worse I had to keep the radio on the same bloody song so he wouldn't know I'd seen!