Probably through the professor’s son’s Snapchat account… 
Joke aside, this issue is very real…
All summer long my daughter tried to arrange a trial lesson with a particular professor and never received a reply. She politely follow-ed up couple times with the suitable gap of few weeks in between and eventually gave up. We met the said professor coincidentally in a totally unintended way but it was past the application deadline and my daughter did not pursue that particular school in the end.
No, we didn’t tell him about it when we met him and yes he was actually a very nice person as we met him and my daughter felt a little bad for skipping that school / professor…