However, do NOT edit that code directly. You could cause irreparable damage to the file. After you find the culprit go to that location (field script, doc-level script, etc.) and edit it there.
I forgot about setting up the External Editor in Preferences -- thanks!
Using a robust text editor like TextPad, NotePad++, etc will have a find feature that could be used. Just do not modify the full file since there are lines of special text that are used by Acrobat to split the big file into the very specific actions.
Using an external text editor will also allow the editing of much larger action scripts since there is no memory space limitation as there is with the built-in editor.