Ouch!! That is a hard one to break. You hit solid. You're right, you probably saved your clavicle by not putting your arm out.
I hope you are better soon and can get back on the trainer quickly.

FYI: As for the jersey, ladies, there are many ways to cut off a shirt. If you have the presence of mind at the time, have them cut near the seam on one side, right up the armpit. Or if you are sleeveless, have them cut along the seam across the top of the arm on both sides and pull it down your waist. Then it can be trimmed and sewn to save the shirt. I learned that from a veteran medic/cyclist I used to work with.

Good luck and feel better soon, MP.