Were you behind a hill and they did not see you? If so, always have a member of the foursome stand atop as to be seen. Not much you can do about this (unless the answer to the next question is no).

Were you caught up on from the group on the tee? i.e. Were they not behind you when you started and then they were playing at their pace (probably a little faster) and just caught up on you? Then you do confront them (assuming they did see you) in a gentelmen's mannor. If they become brash, you simply let them play through and mention it to the ranger/starter.