Sun bleaches scorch marks out of carpet.
In a fit of domestic rearrangement the mat which had been in front of the fire found a new home beside a French door. It’s basked there in sunlight all summer and the scorch marks have faded away.
P.S.
I wasn’t responsible for the scorching nor even at home when it happened but I have grounds to suspect impatience during fire lighting and a bottle of maths meths were involved.