At mt.Ember after you beat the Elite 4, you those rocket team members should have opened a holw in the rock at mt.member enter that place and you should find the Ruby at the end of the place.
i went to the end of the place and i didnt find a pokeball thing i even tried using the itemfinder and it said nope no respone
You wont find a Pokeball
You should find a Ruby
oh i went the wrong path lol so i went the other path and found it