Sometimes the screws arent in the exact bag that you are working in at that point of assembly. What I do is get out a very large size card table or picnic table and put a sheet over it and open all the bags leaving the letter by the bag so I can still identify it. I noticed that the screws are very close in size and length and very hard to tell apart so you may need to search through all the bags for the one screw you cant find. I have assembled 4 or 5 mugen cars and have never been shorted on anything so you shouldnt be having the problems you are if it was a factory sealed box. Fine threaded metric screws that are countersunk can be hard to find so try not to lose any. Building 1/8 scale is fun huh, youll get it and then you can appoligize to Mugen.