Bone or ball

This is his Lordship's new beach toy!!
The problem I've got ( so any doggy help welcome!) is he chases a ball,
Well sometimes.....
He will pick it up, then drop it & then come running back to me with out said ball !!
Sometimes he runs after it & doesn't even both picking it up...
We've tried treat reward, hard balls, soft balls, big balls & soft balls!!!!!
He did pick up Mr bone & brought it back a few times though!!!!
So I guess it's just trial & error!!! :-)