Got your heart jumping with that subject line, didn't I.
Are there any markings? I think your friend is probably right but I am far from expert. What I do know from my own experience is that there are a lot of commercial made packs on the market in cotton webbing with metal fittings that look a lot like 1937 Pattern Haversacks - but were made for sale by camping outfitters. Instead of brass fittings, they have black metal furniture. It would not be unheard of to see something so close to looking military actually be a civilian item. Military items generally do have markings, particularly when in new condition.