Perhaps I am not understanding you but you write:
.....how it would be possible for them to know who gave them extra......"
Presumably you would be handing it to them so, of course, they know it was you who gave it to them.
As ot how do they know your name and/or cabin number.....The stewards on HAL are remarkable about knowing who the pax are. YOU may not realize it but they have a knack (and I have tried hard to learn what it is
) for remembering names/faces. We have cruised many, many times on HAL. More times than I can count, we board a ship and a steward we have no memory of will approach us and say hello. He will remember what ship/when we last sailed with him. They are always correct; When they point out the approximate date and the ship, invariably we think back and they are accurate.
If you have cruised HAL before, I would think you may have noticed this talent most of them have.
If they do not know your name/cabin number, they wll ask one of their friends working Lido with them and one of them are sure to be able to identify you.....whether you know it or not.
(Thank you for your nice words about my participation here.)