If part of the finished baked pizza stuck to the screen, it is quite likely that the dressed dough was stuck to the screen before baking. The usual causes for the dough sticking to a screen is that the screen is unseasoned, or the dough is wet (e.g., with a high hydration), or it is left on the screen too long before baking, or if the screen has baked-on parts of former pizzas, causing the dough to stick to the baked-on pizza remnants. Seasoning of the screen is always a good idea before using it to make pizzas and so is coating the screen with a light oil spray if the dough is a high hydration dough. For me, the hydration cutoff is above 63% hydration. It is also a good idea to have the sauce, cheeses and toppings ready before dressing the pizza and to act fast in dressing the pizza, especially for high hydration doughs.