I think when sam digs up dens body they only find things like:

Shoes
and other things he might have been wearing

The body cant be found because it has dissapered (disintrigated) (WELL WALFORD THINKS THAT) into the cement they layed. And in a few years i think den will return and the storyline will be he came to and left shoes and stuff behind to make it look like he was dead.

This would make a huge storyline

O AND YOU WILL NEVER GET DEN OUTTA THE QUEEN VIC!