A few hours after you reserve a friend’s wish (the exact period is randomly selected each time, and if you haven’t canceled the reservation during that time), the user receives a notification that one of their wishes has been reserved.
The user cannot find out who reserved the wish. The reserved wish itself is also not shown in the notification or in the user’s wishlist.
However, please note that if desired, the user can find out exactly which gifts are reserved in their wishlist — to do this, they can “cheat” and open a link to their profile from another account or through a browser in “incognito” mode.