USTA Section
18. Player shall not engage in unsportsmanlike conduct. During the course of a
match a player shall not engage in:
a. Verbal abuse. Swear at an official, a spectator, or an opponent in a voice
that can be heard by any person;
b. Visible or audible profanity or obscenity. Use profanity or insulting,
abusive, or obscene language in any way that may be heard by any
person or use obscene, insulting, or abusive gestures;
c. Racket abuse. Throw or break a racket other than in the normal course
of play;
d. Ball abuse. Deliberately hitting, throwing, or kicking a ball that is not in
play if the ball:
• leaves the playing area;
• hits or comes close to hitting any person; or
• could cause damage or harm.
You played in a sanctioned USTA tournament, which applied the rule above. For non-adults sometimes the rules appear to be harsh, but younger people tend to abuse the system more than adults, at least IME. I have also seen adults blow their cool, but they normally break things during changeover. Sometimes they receive a warning, sometimes a penalty. Swearing or whining, even against yourself will get you penalties. If you were doing it thru out the match.... It is at descretion of Umpire or Official supervising the match. Just keep your cool. It is a game, not something that involves 'life or death' choices.