Libgdx, tiled map – how to reload layer?

In the simple platform game I’m making, when player collects coin, its cell is set to null. Is it possible to recover all cells from layer “coins” after player dies? I have tried multiple things but none of them worked :/

Here is part of code responsible for collecting coins:

for (Rectangle coins : coins) {
        TiledMapTileLayer layer_coins = (TiledMapTileLayer)map.getLayers().get("coins");
        if(dotRect.overlaps(coins)){
            layer_coins.setCell((int)coins.x, (int)coins.y, null);
            coinsN++;
            Sounds.playCoin();
        }
    }

But when player dies and re-spawns, there are no coins if he collected them before. I tried reloading the map – it works fine, but loading after every death is unacceptable – it takes a lot of time.

EDIT: Now I have another problem, with loading TiledMapTile to put into cell…

TiledMapTile coinTile;

public void show() {
    TextureRegion mapTexture1Region = new TextureRegion(mapTexture1, 32, 0, 16, 16);
    coinTile.setTextureRegion(mapTexture1Region);
}

It gives me NullPointerException, and I have no idea why :/