I can agree to that. The first mission they went through would have to be reworked a bit, and the second could have happened on the way back with a distress beacon, as you suggested. In this case, none of it is going to be vital to the main story, and I don't think we will have to spell it all out in our bios. I think revealing it over time through things like dialogue, flashbacks, and other exposition would be more natural.