Voldemort's Orders re Not taking Harry in HPB

[gelite67]

No: HPFGUIDX 186328

Snape at the end of the HBP:

"Have you forgotten our orders?  Potter belongs to the Dark Lord -- we are to leave him.  Go!  Go!"  Amedican hardback edition at 603. 

I understand why Voldemort needed to be the person to kill Harry.

I also understand that, at that point, Voldemort didn't want to duel with Harry b/c he didn't yet understand why his wand didn't defeat Harry's in GOF.

What I don't understand is why Voldemort would have ordered the DE to  leave Harry.  Why not kidnap him when they had the chance and then keep him prisoner until Voldemort figured out what to do?

Snape seems to be referring to genuine orders.  "Have you forgotten" implies that Voldemort gave the DE explicit instructions in that regard.

If Snape was lying to protect Harry, how would he explain that to Voldemort that he (Snape) reminded the DE of instructions Voldemort had not given?

I suppose Snape could have meant "Leave him to me to bring" but Snape fled when without Harry when Buckbeak intervened.  I can't see Voldemort accepting a hippogriff attack as a valid excuse for Snape not bringing him the Chosen One.

Again, I'm aware of Snape trying to protect Harry.  I just don't see why Voldemort wouldn't have ordered them to bring Harry to him alive, and I don't see how Snape could explain away the fact that they didn't.