All three secret scenes exist! Although one of them is unfair (which is my fault, I plan to make it more obvious in the next update).
Felix's can be found by visiting him at the shop multiple times. Currently, there's nothing to buy at the shop, so I understand why it's hard to find (Once more content is added to the shop, I'm sure a lot of players will get that scene).
The two missing strippers are both Alex. One is Alex with a dick, the other a pussy (Both are completely optional. You don't need to fuck Alex's pussy to see Alex with a dick.)
Thank you for playing! It means a lot.