Was this in 2011 or 2012? If it was in 2011, this was correct.
In 2012, the rule changed. Instead of following the "lateness after 10 minute rest break" rule, which is one game penalty up to 5 minutes late, then default after 5 minutes, they decided (rightfully so) that this was too harsh when you are playing a match tiebreak. When the player wasn't on court at 3:00, the umpire should have issued a time violation warning. At 3:20, he should have issued a "CODE VIOLATION, DELAY OF GAME, POINT PENALTY." At 3:40, he should have issued a "CODE VIOLATION, DELAY OF GAME, GAME PENALTY".
It's in the Friend at Court (page 122).