I've been intentionally staying out of this one, but something to consider:
I have little knowledge of the A320 series (given I work for brand B), but it is normal to provide significant separation between wire bundles to minimize the risk of a single failure taking out multiple systems. So it is reasonable to assume the wire routing to the CVR and DFDR were separated by several feet.
Pure speculation here, but it's quite possible that (assuming a bomb blast), the initial blast severed the wiring to the DFDR - hence no useable data. But some of the wiring to the CVR survived the initial blast. The bomb blast compromised the the fuselage and small debris exited the airframe (such as the unfortunate infant) while the pilots attempted to maintain control of a critically damaged aircraft while donning their oxygen masks (far too busy to contact ATC). Despite their best efforts, within a minute or so the aircraft completely broke up.
Again, purely speculation on my part, but it does fit the known data rather well.