I've Got Your Number by Sophie Kinsella

I’ve lost it :(

The only thing in the world I wasn’t supposed to lose. My engagement ring. It’s been in Magnus’s family for three generations. And now, the very same day his parents are coming, I’ve lost it. The very same day. Do not hyperventilate, Poppy.

Stay positive!! :)

A couple of glasses of bubbly with the girls and Poppy’s life has gone into meltdown. Not only has she lost her engagement ring, but in the panic that followed, she’s lost her phone too. When she spots an abandoned phone in a bin it seems it was meant to be . . . Finders Keepers!

Except the phone’s owner, elusive businessman Sam Roxton, doesn’t agree. He wants his phone back, and doesn’t appreciate Poppy reading all his messages and wading into his personal life. Can things get any more tangled?