looking for people with the id number

[Palmarina]

Hi, I have a question. Looked in the rules but could not find any help.
I received 1 FC from a neighbour when opening the Farm Pass. By the time I wanted to thank that person I forgot the name. Looked in My account and found the ID number.
Now the question: how can I find that person? Where do I fill in the ID number to look for him/her and send a thank you? I pasted that number in the facebook search field but without any result!
Please advice.
Thank you in advance.