There is an common mussar shiur about where ever you are Hashem is watching, So even if you do an averiah in Public and nobody seems , Hashem sees.
Today with Smart Phones, everyone has a portable video camera, Everything you say and do can be videoed and put on you tube. You should always watch what you are saying, you never know when someone is taping you and going to put it on youtube. You should doublely watch your speech and actions.