Does Black have a win in this position? I was playing a game as Black against computer and came up a tactical move that defends me from pressure. I have expected a normal retreat of the queen yet computer kept sacrificing the knight like it was lost anyway, therefore this question :

Did I miss a win for Black or the position is just fine for White?

Here is the position:

[Title "White to move"]
[fen "4r1k1/3q1ppp/pp6/2QN1n2/1P6/8/P4PPP/3R2K1 w - - 0 1"] 


White kept playing Nf6+ or Qxb6 but I believe that any retreat of the queen is fine, what did I miss?
My suspicion is that the computer is calculating at a depth of 3-ply. At 3-ply depth, it sees that the following variations are winning - 

1. Nf6+ gxf6 2. Rxd7 and 

1. Qxb6 Qxd5 2. Rxd5

winning material. 

If it was at 4-ply or more, it would have seen 2...Re1# in both lines and rejected those lines. 

To answer your question, no, Black doesn't have a win in this position. White can play 1. Qc1 and white is fine.