*(The image attached is off of google and for reference only)*

Recently I spoke with my older brother with whom I used to play Minecraft all the time when we were young and he made a comment that unlocked a bunch of memories of the first world we ever played together in.

 We were reminiscing on our massive builds and the industrial amount of TNT we unleashed upon many villages but then he mentioned the name of the world. 

"Harlem Shack" 

He started teasing me for misspelling the name of the harlem shake meme but I let him know that I wasn't the one who named the world and that I always thought he was the one who created it since's the one who installed the game on the family pc and I assumed he created it while testing if everything worked. The conversation moved on but the confusion stuck with me and I remembered something else, the first time I booted up the game I spawned underground in a base. I don't remember much of it, just that it had cobblestone walls with torches and glass windows and a door that looked towards a cave, I couldn't find my way out so I switched to creative and started mining upwards until I got out of there so I could actually start playing. 

I was never able to find that cave again, even though I did search for it multiple times after

The launcher we were using to play was unofficial and so I don't discard the possibility that it was some sketchy spyware or something, but I find the idea that it also could've come preloaded with someone else's world file really strange, yet I'm 100% sure I did not create that world. 

Did anyone else ever experience something similar? This would've been around 2013 and I'm pretty sure the version of the game we were on was 1.7.2

[QUESTION] World save included with old unofficial launcher?