My MMR from normals to ranked.

I am currently playing my placements for ranked, and found I had lost most of my games. Why? Because in normals I got placed against bronzes, destroyed in mid or top, and easily won the game because of it. When I go into ranked however, I see loads of gold and silver borders. I haven't practised against gold players in normals and therefore get crushed by my lane opponent, go 0/12 with 20 cs at 20 mins, and lose the game with my whole team saying 'gg mid fed' please can anyone tell me if this is a bug or if riot actually wants players playing in ranked at a skill level they can't practise on.