Game crashed after save, I'm scared

Hello. A few hours ago I was in the Happy Home Showcase visiting the houses, and I saved the game with "Save and continue" option to continue playing later. Then, after save, when the screen turns black before taking you back to the game, the game closed with an error message. Immediately another message appeared saying that the console couldn't find the SD card. I have ACNL in physical format. I know about corrupted saves related with closing the game while saving, so I get scared. After restart the console, the SD card was working. When I started the game, Resetti appeared. But the game was saved. The game crashed after save. I don't remember anything like this happening to me. The game saves correctly, but I'm scared with this error and if it can happen another time while saving or if the game is damaged. I have 500 hours in ACNL and started playing in July 2013 and i don't want to lose my progress. Does anyone know about this error? The message didn't specify the cause.

Sorry for my bad English, I'm Spanish.

I had that after my DS fell on the floor (landed on carpet, and didn't fall far) It doesn't take much to jar the SD card loose.
I undid the screws (Google it) and took out the card, wiped it clean, and put it back in.

The 'couldn't read data, or find card' (can't remember word for word) error was gone.

Now while I was going to the Main Street the console stopped working and showed this error (The photo isn't mine, is from Google): https://goo.gl/eS3rbE I restarted the 3DS twice but the SD card wasn't working. I extracted it and I blow. Now It's working again.

I'm almost certain that the fault of this errors is the SD card. I'll copy the data and tomorrow buy another SD.

My error was a popup. It couldn't read/find the SD.
My 3DS XL is only 4 months old, but I did drop it.

This has happened to my SD card and how i fixed it was to unscrew the back of my console and take out and clean the SD card. My SD card has been fine ever since then.