99.9% of people that find phones do not know how to do that. Implausible at best.
He was in the restaurant to do a Bitcoin deal. So the guy at the same table as him likely knew how to do it.
I think that's where I'd start my investigation if I was him.
Wait up. Can we catch the thief? What's the btc address sent from and does the receiving address match any known transaction thread post?