I got 3 hazelnut trees from Willis Orchards, and the roots had been almost completely cut off. They were just nubs maybe an inch or two long. The trees were 1/2 inch caliper, about 5 feet tall.
Can hazelnuts regrow roots after being cut off like that?
Okay, found it. These trees were all about 18 inches tall. I can't point out which were the hazel, but I have 4 of them. Not all of them made it into the picture. I kept the in pots their first year here. Gotta get em in the ground soon.
I would second Steve's suggestion to cut the tree top growth back to just a few inches when planting. Hazels generate well from coppicing (at least the UK varieties do here). Not good to have cut all the roots off..... I would take a picture and send it to the nursery, maybe there is still time for a replacement to be sent. As long as there are some thread roots they do have a chance though. Plant them a little deeper than they were growing and keep them moist through the summer if you can. Have you some fungal innoculant to put in the soil when you plant them? That should help get the root-soil organism network started. A little soil from around a local healthy growing hazel would be best for this probably.