Why don't you just ask your FM the one who got switched to Captain to switch back??
Because to be honest the fact that you said it just switched sounds a little fishy to me, Also if its accidental they might not switch it back as well.
The problem your friend is referring to about it not working when Disbanding is where the database doesn't actually remove you from the crew even though it looks like you have just left it but that can be fixed by a CSR because I've had the problem a few times myself.