Great fight! you rolled a 3, you get no special field bonus's for being a thief, but you posses Grub! +2 to all rolls (giving you a total roll score of 5). You took down the Water Demon who only had a power score of 2.
You still have 3 life points: 
You have Grub in your inventory 
and when the next Stage is available may continue. Well done!