Sorry society I have only just seen your post.
One must assume that the patient has survived the cardiac insult.
Now if a small, less important blood vessel is blocked and the collateral (subsidiary) vessels help out, then the scar will be reduced to a minimum, but if a large vessel is involved, there will always be evidence of this on an ECG.
Of course, at post mortem, the scar would be obvious either on direct vision or microscopy.
So ...yes.....once the heart muscle has sustained a scar it remains....if you look in the right place.