The kindergarten teacher touched the children's buttocks. Can you extract fingerprints from underwear?

Of course. Fingerprint is actually an imprint formed when a person's finger touches the surface of an object, because the finger has uneven lines, and secretions, sweat glands, dust and stains attached to the surface of the finger or object are separated by lines, just like stamping. If those foreign objects are covered or destroyed by the environment, it is impossible to obtain fingerprints.