Almost certainly not. Consider the furore had it been introduced as evidence.
The USSS story is that they cooperated with the FBI, who was in charge of the investigation, and submitted all their evidence accordingly. Consequently, the FBI -- for reasons undisclosed (but highly suspicious) -- must have withheld this evidence from both the prosecutors and the defense.
I wonder who might've made such a call...
I didn't think so, and do not recall it being brought up at McViegh's trial.