you're correct, but an entry in mirc.ini does NOT convey any information about its state: not existence, size, or if it is currently loaded.
You only asked to know if it's loaded. If the file is currently loaded, it's listed in mIRC.ini. If it's unloaded, it is not. That was what you asked about. The only way that isn't correct is if mIRC itself isn't running, or if someone edits mIRC.ini while mIRC is running (not usually a good idea), or if you are checking the wrong mIRC.ini file.
If you want to know if the file exists or the size, you'd have to use commands either in mIRC or through Windows to determine that information. From within mIRC, $file(filename.ini) will return the size (in bytes) if the file exists or NULL if it doesn't. That solves both of your secondary questions.
