Those calls from home when you are really helpless to do much are so infuriating. I have received a few in my days.
Since we don't know what you are going home to, I can't help much. Maybe make both of them have a "time out" in separate areas and you can talk with them one on one to get each story without the other's interruptions?
A suggestion for the next emergency time when the oldest has to watch the youngest, would offering a movie-a-thon work out? Let the youngest pick out some of his favorites (or rent ones he hasn't seen) (that are age appropriate of course) and let him watch the movies while the oldest is there just for supervision?
It doesn't always work out, but having some planned activities for the youngest sometimes helps a lot. When my difficult child was 10, he liked painting projects (bird houses) if you are brave enough for him to paint while you are gone. Or lego sets, or gather cardboard boxes and markers for coloring projects - if he has a car collection he can make a "town" on the cardboard boxes - draw roads, businesses, ect. - if he has animals, then he can make a zoo.
Here is hoping it is not as bad as it sounds. Atleast you know SOMETHING is up! Ugh big time!