I'm assuming you are playing your placements? Even if you have and another 10 or more games in this may still apply.
As an unranked player, your mmr does not start at zero. Rather the system assigns you an mmr (when we used elo it was 1200, and mmr is similar just modified). Other players who were ranked previously underwent a 'soft reset' whereby their mmr gets partially reset based on a formula (I believe that formula is End of season mmr plus 1200 all divided by 2; or (MMRend + 1200)/2 ). Now, 1200 mmr is pretty much silver 5. So silver ranked players can easily be brought down to 1250, 1300 kind of level and run into brand new players. Golds can do the same thing, especially if they tnked following end of season (what the borders are based on) and end of preseason (what the reset is based on) (i.e., they may have been gold for a border but lost enough mmr to be silver anyway.
The bigger thing that likely is causing you to lose lane is that norms and ranked are different beasts. Just becasue your play style worked for norms doesn't mean it will work for ranked. Also, your normals mmr is separate from ranked. Therefore you may actually be a 1000 mmr player (or lower) and the ranked mmr system just hasn't got you down to where you as a player 'belong'.
TL;DR - doesn't sound like a bug.
Keep your chin up, try to improve, and try not to get turned into a dick by the toxic people you will inevitably run into in ranked.