A bit odd that they didn't include Japan in their set of countries. My expectation is that it would have probably topped the list.
We originally planned to include Japan but after some initial pilot testing we realized that the country was unsuitable for methodological reasons. Japan has a lot of small “police booths” where people can return lost objects. During our pilot tests, we found that Japanese citizens would not contact the owner but instead drop them off at a nearby police booth. This feature made it virtually impossible for us to assign individual wallets to particular drop-off locations.