Hello, i got the same bug yesterday and submitted it on the discord. Turned out its a known bug and it will be fixed or the public release, according to Marcello.
The best you can do meanwhile is to load an early save, before you ever spoke to teddiursa for the first time. Save right in front of him an try/retry the event until he does not hide within the garden. If i'm correct there are 7 possible location and he will only use 5 of them, so it shouldnt take too long. Took me 4 tries.
Good luck !