About 2 years ago, I bought a Rocket League disc that was the legendary edition. The legendary edition came with all the bat mobiles and other stuff. I just noticed that I don't have the bat mobiles anymore. I remember seeing them a couple of months ago before Epic Games bought Rocket League.
I also decided to buy the digital version of the game because it was free, so I didn't have to use my disc. None of my items I had were gone except the bat mobiles.
I don't know if Epic Games took them away or I need the disc to get them back.