M. Night Shaym-Aliens! - How Rick knew

I just watched that episode and payed attention to find out when and how Rick found out that they were still in a simulation. I think it was when they rescued Jerry. Rick asks: "Why are you dressed like a waiter?" If this was reality then that would mean that the aliens abducted Jerry while he's wearing that suit. Why should Jerry wear a suit while sleeping? So the suit must be simulated which means they are still in a simulation. When they're finally in reality Jerry is only wearing his underwear. Rick is wearing his clothes, because he probably fell asleep drunk somewhere before being abducted.

Now what would still be interesting to know is when and how Rick found out that Morty is part of the simulation. But, maybe he thought from the beginning until the end that he was the only real person in the simulation and was kinda surprised to find out at the end that Jerry was also real.