['I am incredibly lucky to have a stranger return my new phone when I lost it on the bus.', "That is extremely lucky.  It's nice to know there are still good people in the world.", 'For sure. I had already written off finding my phone but this random person sure surprised me!']
Wow.  That sure saved you a lot of money on replacing a phone, too!
I am incredibly lucky to have a stranger return my new phone when I lost it on the bus.