Hi, I play minecraft on a laptop in browser because I could not find out how to download it...(It wasn't working)

Anyway unfortunately my laptop failed on me yesterday and the only available option was to wipe the whole lot back to factory settings. Which reset everything and was like starting from new.

Now seeing as I played minecraft online and in browser and you have to log in I assumed that my worlds would still be there... Apparently not.

Is there any way I can get them back at all? Kind of pissed off, just had built a castle and found a big cave with diamond in lol :(

Thanks in advance, and p.s does anyone know how to download minecraft and what programme you need to use to run it?

Thanks alot! Tom.