If you can't find a function in the list of functions and your app is proguarded, then the Proguard might have made your function inline. You would not be able to apply a patch on the missing function for this apk.
You may want to set things right for the future versions. You can switch OFF the function inlining optimisation of proguard by adding the following line in proguard rules (proguard-rules.pro) of your module.
Check out the optimisation related documentation of Proguard for more details.