I have never worked on an 024 saw, but I have worked on others and some Stihls at that, here's a parts diagram of that section , hope it helps, might have other members with experience on your model chime in before long, .....
View attachment 40172 ... click to enlarge
The diagram solves it...Part # 14 : It goes between the two halves of the air filter. I can't believe I didn't remember this after disassembly..! Thanks.....