Originally posted by pipo.p:

According to file dates, the game has no such autosave. Only (auto) worldsaves, like on every half hour, and a save on disconnecting. I'd be curious to know if the date of the last saved game in your save folder corrrespond the time when you Alt-F4ed.

it definitely does. try it, destroy or build some stuff in your world. close the game via alt f4 or task manager. your world will have saved what happened moments before