If you are lucky enough and your applications appears on the list showed by the regapps inspector you have done. In that case you don’t need to look for a path.
Open the qna or the FixletDebugger run the relevance expression regapps and see if the applications are showed in the list. In that case you can use something like:
exists regapps whose ( name of it contains “myappname” )
Otherwise you need to use the path of the installation but it may be not so reliable because the user can install the application in a custom path and it may depend on the OS version.
exists folder "C:\Myfolder"
exists file "file.txt" of folder "C:\Myfolder"