My co-worker should have had guts to say "No", I don't know what I am doing and I don't want to poke around when I am in the middle of some other project and it's late at night..

Or at least keep other programmers in the loop and ask for advice. I cannot blame only our boss. It's maybe 70% boss' fault and still 30% of my co-worker. You've got to have guts to say NO.