If its only one cushion I would take it away and have a go at it in private.
From what I have heard over the years, this will probably be permanent damage, sorry .
But you never know, nothing to lose, so take it away and try a few things on it ?
If the worst happens, remember, you are only liable for the " current value" of the item, you dont have to buy them a new suite !
Good luck , it always happens at Christmas time !
Chris