As BladeTiger said your antivirus probably deleted the file or something but i can ensure you that the dll is in the folderQuote:
If I wrote it, it's because it's not really inside. These are the files inside the folder with and without unpacking:
Bt12 TCPClient.au3
Client_PacketLogger_Test.au3
PacketLogger_API.au3
Qt5Core.dll
Qt5Gui.dll
Qt5Network.dll
Qt5Widgets.dll
and the platforms folder contains qwindows.dll.
Trust me, there is not Packetlogger.dll file.
EDIT: I renamed .au3 files into .dll and moved into GF folder with ->other .dll files<- but when I click on GF client it doesn't open. Seems that it check original Qt dlls are changed.