This actually is not how it’s supposed to be and it is fixed on the next patch.
Look at Rocket being nice again
When is the next patch be out and will we get red gardevoir as mystery gift or 2nd or 3rd time against rematch elite 4 ?
I don’t have a release date for the next patch yet. I’m diligently working on it just about every day but there are a lot of bugs that have been put off and need to be fixed before I’m satisfied with a public release.
If you’ve defeated the Elite Four without losing any Pokemon on your current patch then you won’t need to worry about doing anything else to get the Red Gardevoir when the new patch is released; the same guy will give them to you immediately and he won’t disappear this time.