Yes, it can be disheartening when someone you have a strong communication bond with starts to change and act as if they don't care about your existence. It can be bothersome and leave you feeling disconnected and uncertain about the relationship.
Sometimes, you will be asking yourself what you did and where you got it all wrong without knowing the answer. Life where someone you used to talk to almost every day, changing to where you can't talk to them anymore, can be strange and confusing. You will keep asking yourself what you did wrong.