Please go ahead and give her food and water now. No need to withhold them. Cragg is just wanting your to check the crop eatly in the morning before she gets a chance to eat or drink when the crop should be flat and empty. If it feels full and hard or puffy, then that is abnormal. Since you could not feel anything, it probably was empty. So now, you can practice feeling crops of the other hens, and if they are eating, they should be felt easily during the daytime as they fill up with food and water.