The enhance reads
E commit: Add one non-attack block from your discard pile to your hand. If you do not attempt to block this attack with the card you added to your hand with this ability, discard your hand. Only playable during your opponents attack.

Today we were playing and my opponent aborted the attack. Do discard my hand? Or does the the discard part fizzle because there is no attack to block anymore?

No, you don't discard your hand, because you never get to the block step of the attack.

can we get a mod to stamp or confirm?

If there's no block step, VotL's hand discard pretty much fizzles as you never reach the point where it would check if you blocked with the card.