Can I keep my drywaller's scaffolding that was left here?
Why don't you want to return it?
I want to use it in the future.
If it doesn't belong to you then you should not keep it. Return the scaffolding to it's rightful owner.
I just don't want to return it.
I can understand that it might be out of your way to return the items, but it is wrong to keep others things. The person might be able to use it on another job without having to pay more money.