? Finding contact / connection in order to block the person

Hi! 

I need to block a person from possibility to view my activities on Garmin but I cannot find it on the list, as he is using quite common name / nickname "Stone". When I write the name to finder, it starts to show me the list of persons starting with A in the first name, but the furtherst I can get is on R in the first name, and then I reach the end. It doesnot offer anyone just with the nickname or name Stone - I suggest there is some restriction on numbers of connection shown. 

Is there any hack how I can see just the person with accurate name/nickname? 

Thanks for any suggestions.