You lucked out man!  
As a former firefighter, I’ve seen a lot of houses go down.  You were lucky.  I take it the FD was there already, protecting your house?
Depending on your surroundings, the fire could be smoldering underground for days.  I would keep a close eye on things, especially on the edge where the burned meets the unburned.  The FD is most likely doing this, but sometimes they don’t do a perfect job; I wouldn’t bet my house on it!
100 acres?  Holy cow!  How many do you own?