The one that you bought dosen't have a bolt hold open does it?
Your right it doesn't. I thought that was odd.
I remember when I first got my SKS. I was trying to put the trigger group in and I had the safety off.

Well I am sure you can imagine how comical it was to see me trying to put that dam thing back in. I was hoping to not make another simple, yet fustrating mistake.
So does that button double as the latch it's self, like that latch that holds in the trigger group on the SKS?