Why would they not do contrast on MRI of foot when planed?

If "planed" means "planned", then probably because they misread the instructions, or there was some counterindication (such as an allergy to the contrast agent, or kidney impairment) making using it problematic. Or possibly the doctor didn't feel the contrast was necessary... contrast agents are commonly used to increase the contrast between various types of soft tissue to find (for example) leaks in the blood-brain barrier, lesions in the liver, or other conditions unlikely to be found in the foot.