I can't reproduce it.
Could you please provide the steps to reproduce it?
My steps were:
1- Open an existing Solution
2- Add An Existing Item to the Solution (the llblgenproj file)
3- Open the Find in Files and look for "Customer" in "Entire Solution", no specific file extensions.
Search completed without opening the llblgen project file, either inside VS or in the LLBLGen Pro Designer.