Yay Lucy girl! We knew you would do it sooner or later. That's what our trainer told me too that some small dogs just never get the down command because they are already close to the ground..lol. But I kept trying and same as you - the lightbulk moment - and all is good.
The one trick that's hard for us now is the roll over - she just is having a hard time with it and if you get any suggestions let us know.
Glad you like your training - we love it to - it's fun.