My understanding is tht Christopher Wray, director of the FBI, stated that they didn't know if President Trump was hit by a bullet or shrapnel. Following the hearing, the FBI put out a statement clarifying that President Trump was, indeed, hit with a bullet. I don't recall any questioning of the nature of President Trump's wound during Wray's testimony, only his speculation that it might have been shrapnel and not a bullet which was clarified by the FBI following the hearing - that President Trump was, indeed, hit by a bullet.