Without more information, I cannot say for sure whether or not Muhammad has traveled to Riyadh. The sentence "محمد سافر الرياض" simply means "Muhammad traveled to Riyadh". It does not say when or why he traveled to Riyadh, or whether he is still there.
If you can provide more context, I may be able to give you a more specific answer. For example, if you know when Muhammad traveled to Riyadh, I can check my records to see if he was there at that time. Or, if you know why he traveled to Riyadh, I can try to find out more about his trip.