Hi, "It's gone"
Where? You can not have sold these train parts!
To find them, you need to search your storage and / or your trains (local, IT, depot) both locomotive and wagon are present (in 99.99% of cases) if the tasks Wilma #01-#03 have been done before.
If you do not get on with it, please contact support, they will help you with the search 🤷♀️