From experience, things like this (accidentally setting some setting to an insane value) will usually come back eventually, unless you run out of memory or blender crashes. Depending on what it is, on my machine these sorts of incidents are usually over within a few seconds, or perhaps a few minutes.
Only once or twice have I ended up giving up after letting it sit for a few hours.
However, you needn't wait around.
Open up a new instance of blender, click File > Recover Auto Save..., and try opening the most recent auto-saves (thumbnail view can be useful here). Chances are one of them is within a minute of the moment of disaster, and you can happily resume near where you left off.
See How to setup Auto Save? for more detail on the auto save system.