Same thing happened to me once, I had requested double boxing and seller said no problem but sent the item single boxed. However it was so very well packed (must have been a mile of bubble wrap in there) that I went ahead with a positive.
If it was well packed, I’d give your seller a positive. But if it wasn’t and only got to you in one piece by sheer luck, I’d go with a neutral and a warning “got lucky with the shipping but not properly packed”. Or something like that.