No, that wouldn’t likely be possible. Game Masters are mostly hands off when it comes to achievements and achievement credit. The only time they are able to grant one is when they have specific policies and procedures that allow it.
This is not one of those at this time, as they are planning on a fix to help resolve it and allow folks to collect them as intended.
will it be achievable after the bug is fixed? the event ends tomorrow
I don’t see any conditions on the achievement that says “during event” so it is likely still going to be possible. As noted in the update posted here, the cards will continue to be obtainable after the event.
Players can now collect missing cards by using the Hearthstone Gameboard toy to defeat others in a friendly game. It will continue to drop cards after the event ends.