What your child suffered was a stroke due to blockage of the deeper arteries of the brain that supply a collection of cells called the basal ganglia. I am confident that the fall was a coincidence. This is not an uncommon problem in infants and toddlers. The good recovery supports my feeling that the basal ganglia were affected. There is excellent chance that this will not recur. You should encourage physiotherapy and avoid massage.
We have not consistently found causes in our patients with similar events. But I would recommend the following tests:
PT; PTTK
CBC, Platelet count
S. Homocysteine
Antithrombin 3
Lupus Anticoagulant
Anticardiolipin antibodies
Protein C and Protein S estimation