If he's still a destructive chewer, then you need to continue leaving things out of reach. I've had puppies that were completely reliable about not
chewing by 3 or 4 months old (Dena!
), and others that can be relied on to
chew certain things, even as old as 4 years (Halo!
). This is what she was up to Christmas morning:
She also likes toilet paper...
And kitchen knives!!!
She doesn't care about shoes, socks or clothing, pens, coins, or the other usual stuff that ends up on the floor, but if it has ever touched food - watch out, lol!
She used to have a thing for eyeglasses, and TV remotes too.
If I had a 9 month old puppy in the house I would make it MY responsibility that everything was put up out of reach, especially things that belong to a guest that may not realize that puppies chew. I do think it's unrealistic for your friend to expect him to know his boundaries - training is a process, and it takes time and patience.
Cassidy was our worst chewer, she literally couldn't be left alone for 5 minutes or she'd have destroyed something - she ate one of my orchids while I was at work and my husband was on the phone in the office, she chewed a hole in our blanket and ripped up our quilt, (again, in mere minutes), she even took down the slippers I'd put on the bathroom counter before I got in the shower, and chewed those up before I got out and caught her. She even had a secondary chewing phase that occurred months after she had improved to the point where we didn't have to watch her every single minute, and chewed a quarter sized hole in the edge of my favorite rug.
I rolled up the rug, and it spent the next year on top of the bookcase because I wanted to make COMPLETELY sure she wouldn't ruin it further. But even she eventually outgrew the chewing.
With every one of my dogs, I put things up out of reach for the first few months (or a year or more, depending), supervised well, and left out plenty of toys that they could play with or chew on. I've never done anything more than that, except for an occasional verbal correction and a redirect to something more appropriate, to teach them boundaries, but they eventually all figured it out. Well, except for Halo, but she's pretty predictable so it's manageable.
Either your friend has never had a puppy before, or she's had puppies that aren't natural destructive chewers. Keep doing what you're doing, but maybe supervise a little closer and do a bit better about putting things out of reach.