The
Grenade Launcher will be scrapped after battle. This is in contrast to
Fusion Borer, which would stay on
Cerebros after the attack.
This is due to a change in language as the game evolved. Early on, WotC used language like "After the upgraded character attacks -> Scrap this card.". Later, they adjusted to "When the upgraded character attacks/defends -> Scrap this card after the battle.". This newer language ties the scrap to the more common "When battles" trigger and not to the rarely used "After battle" trigger".
The same is true for other older cards like
Evasive Maneuvers,
Blast Shield, and
Power Punch, vs newer cards like Emergency Barricade and
Crystal of Power.
If, when defending, you upgrade Nautica with an Emergency Barricade, it will remain on her until the next time she defends. This is because the 'when defends' event has already happened before Emergency Barricade was played. If, when defending, you upgrade her with
Crystal of Power, it will remain until the next time she battles.
If, when defending, you reveal
Bolster to upgrade a character with an Emergency Barricade, it will remain on them until the next time they defends. This is because the 'when defends' event has already happened before Emergency Barricade was played. If, instead, you had upgraded with
Crystal of Power, it will remain until the next time the upgraded character battles.