You can do a scratch test. Test some of the limbs first. Take your fingernail and gently scratch off the first layer of bark. If it is green underneath, it is still alive.

And if it has formed buds at the tips of the twigs, and these buds are not dry, brittle, and fall off when you touch them; then it has potential shoots for next spring.

if it is a plain old RBud ... it may sprout from the ground sooner or later.. or in spring ...

if it is a grafted plant... and it sprouts from below ...it will not be the cultivar you bought.. but a plain old ...

if you have a warrantee ... exercise it .... and learn about proper planting times.. and proper watering ... ask for re-planting in late September or early April in z5 ...

if the seller balks.. offer to take a smaller tree ... smaller trees transplant easier.. and 'establish' faster ... and can easily outgrow a bigger transplant in a given ten year period ...

ken