You should do something like Vee41's idea then.
Using an array could be another idea since you can save a whole array in webstorage. Just create an instance variable on the enemies called ID, and in the editor manually change that variable for each enemy: 0, 1, 2...
Then when you kill an enemy, set the array's X (get the enemy ID) to 1.
And when you load the game, on layout start you can add the Array condition "Compare X" with the enemy ID.
Anyway if you don't understand it I can explain it better, it's something I use in my game to save data.
To save an array use this simple method: http://www.scirra.com/forum/copy-an-entire-array_topic53153_post332888.html#332888Xavier2013-03-17 07:30:54