Terrain data is missing

I was working on a project in Unity 5.5.1 , I created a terrain and transform it into an offroad area for a game. I completed the environment and closed the project. But when I reopened it next time, in my scene the terrain is not visible and terrain data is missing. The terrain data which I had renamed it as offroad terrain is existed in the project but its like a corrupted file or not recognizable in Unity. Please help me to fix this problem Because I have spent a lot of days to build this project. I am attaching a screenshot of this issue, please have a look and suggest me to fix this. Thanks

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Where / when did you rename your terrain data asset? If you rename files outside of Unity it will break all serialized asset references. You should never move or rename assets outside of Unity. However in this case you can simply drag your terraindata asset back into the slots in the inspector. Keep in mind that both, the Terrain script as well as the Terrain Collider has a reference to the terrain data asset.

@Bunny83 I had renamed it in unity editor before I starting to sculpt it. I am facing this problem after I completed the project and reopened it.

I have the same problem. Did you solve it?