As Sarah says, they don't need to recover the body if there is other compelling circumstantial evidence to indicate (i) that the victim is dead (ii) that it was an 'unlawful' death and (iii) points to the guilt of the accused.
There have been lots of cases where things like bone fragments and bits of false teeth have been used to convict someone of murder, I don't know what evidence they've found but if they think it's sufficient to charge him with murder now (rather than say child abduction and wait to gather further evidence) then it doesn't look good 
Edited: 08/10/2012 at 14:28