I obtained a firestone from completing a quest. In a trade, I thought it could be attached to a pokemon by right-clicking on the stone and applying it to a fire-pokemon. I did this on a vulpix, which uses the stone to evolve. Realizing my mistake after the screen asked if I wanted to evolve the pokemon, I clicked no, so the stone would not be used. However, when I checked my inventory, the stone was nowhere to be found! Below is the Vulpix:
Hello MartyMcfly111255, When you use a stone to evolve the Pokemon, it is like giving it to the Pokemon so that it evolves. Cancelling the evolution simply means that you've already used the stone but the Pokemon won't evolve, it still uses up the stone. Sorry for the inconvenience, if you have any questions feel free to message me on discord or on the forums.