Fired up ye old XBOX ONE “S” this morning, logged into my season 25 character and was surprised to find all of my follower items missing. This looks like a total reset of the follower (except the skill choices remain).
Although I don’t play on Console, I thought I’d provide a link to the following topic:
That topic is 2-year old, but it may provide some explanation for what happened.
As far as getting the items back… I’m sorry but, unless you have your game data is saved on a cloud or on some removable storage device, I don’t think you will get it back.