Major flaw in the plot

Rating: 7/10 (4 January 2016)

Major flaw; The crew has left Mars and is 4 months en route to Earth. Mark's survival is known to all on earth for the last 2 months. The crew are receiving periodic updates from their families. How come they don't find out via their friends and families that Mark is alive?
If the crew knew this 2 months into the mission, they would have turned around and executed a rescue mission.
This is such a major flaw that it upsets the entire plot.
What are we going to do about this?
Can I get a refund?
Or can I sue Scott Free productions ;)