I don't think I deserve a medal for not using an engine in this particular game jam. What does an engine do for you? Mostly provide you with a visual scene editor, collision detection physics and a ready-to-use rendering engine. I didn't really need a scene editor for this game, the physics for my game idea were very simple and getting an engine like Unity to adhere to the stringent graphic restriction of this jam was likely more work for some people than just rolling their own.
I in fact believe I saved time by not using an engine for this project. It certainly helped me to work with the restrictions instead of against them.