If you suspect that mold has been painted over, there are a few ways to check. First, look for any visible signs of mold growth, such as discoloration or spots on the paint surface. Second, smell the area for a musty odor, which is a telltale sign of mold. Finally, use a moisture meter to test the area for high levels of moisture, which can indicate hidden mold growth behind the paint. If you find any of these signs, it's best to have a professional inspect the area to confirm the presence of mold and determine the best course of action for removal.