You seem to be having trouble with this. Does your species normally throw things?
Ouch! No. When we get a hold of something, we try to keep it.
Humans do well with balls. They catch on and start playing and having fun in minutes. Ah, well. If one method of training doesn't work, try another.
I'm all too familiar with this type of training. The carrot has failed. Now it's time for the stick.