Without its crown, I am afraid your tree is in palm tree heaven. The crown will not grow back nor will the tree branch.
What kind of date palm is it - is it a canary island? is there any sign of rot on the inside of the trunk? Sudden crown drop on date palms can be due to a deadly disease that is fungal (Thielaviopsis paradoxa) in nature. I have read that drought stress can make palms more vulnerable to infection. For more information on this disease that eats away palms at their core, go here: