Missing saves (Minecraft)

I didn't understand what happened.
In general, I made a card for a friend. For passing. And due to weighty coincidences, electricity was cut off in our microdistrict. After they cut it in, I went on to do it. But instead of my preservation - emptiness. I did not understand, I went to the root folder, then to the folder with the proud name "saves". And there is a save. Strange, isn't it? Moreover, the map itself was voluminous - here you have a huge city, a railway and a highway, and other joys. And they just forgot, that's all.
What can be done besides creating a new map?