I am dealing with a Flash file which has been created by a third party. It has a lot of folders and files in the library and I can't seem to find any ActionScript anywhere.
Is there a simple way of finding the location of ActionScript when the author has been naughty and not labelled it or put it in a sensible place?
I would export to swf then open it with a reverse engineer tool (like Sothink SWF Decompiler) and look through all the scripts/actions. The action name will tell you where to find it if you still need that (you'll see the decompiled code).
You can try the Movie Explorer, Window -> Movie Explorer, or ALT + F3 in Windows. This lets you explore all assets that are added to the stage in a tree like fashion. It wont show items that are dynamically added from the library, but it might be a good starting point.
In addition to @grapefrukt's answer: Make sure you toggle the ShowActionscript button in the Movie Explorer. That would be the third icon, the one with the blue arrow.
You can use the Find field to look search for common actions like: stop(), .visible, etc.
Alternatively you can use the Find And Replace Panel (Ctrl+F / CMD + F) and search for Text (common actions) and tick ActionScript only.
Note: The Find And Replace Panel is a separate panel, do not confuse it with the Find And Replace functionality in the Actions Panel.
Also, I think you could find actions using the Script Navigator, inside the Actions Panel's Toolbox:
HTH