Was Neville caught by his own trap??
I was always under the belief that Neville, himself had set the trap that caught him.
I figured he had previously set traps all over NYC.
At the time he was caught, he had gotten delusional, as you could, and he put Fred there, previously.
In a moment delusion (fantasy), he walked into his ow trap.
I never gave it a thought that the infected could have possibly set such a complex trap.
They didn't have the mind, or dexterity or "calmness" to accomplish that.