he needed to do those steps before buying
- Click on the "Help" option located in the upper left corner of the Steam interface.
- From the available options, select "Steam Support".
- Locate and choose "Party Animals".
- Select the last option, which states "I want to permanently remove this game from my account".
you can try doing it now and after those steps go to support page again and click "It's not in my library" and there should be an option to restore it
but better write to support first, i didnt have this issue myself