I agree with David and James [in particular James's reply]. I think if you do what Christian says you will just get the same answer as the others state.
In the method chapter, you should explain how you dealt with missing data .and in the results chapter ,you should provide a numeric explanation of your missing data in details
We have different format in writing research but base on my own experience in our institution, we can discuss well the missing part of your data collection in your chapter methodology, you may add it also in your scope and limitations (Part of our chapter 1), we can also include that in the recommendation part meaning what to improve the next time around.