Do not aspect that the usercompletes or cancels the search...
Simply add a step to the script of the Main Menu button that checks for being in FIND mode or not.
Look into the Get ( WindowMode ) script step. You can use this on your second button's script and have it only run the rest of the script if in browse mode.
Or you can simply start your main menu button's script with Enter Browse Mode. If the database is already in browse mode, nothing changes. If they are still in find mode, the find is discarded, browse mode is entered and the script proceeds.
Thats not the best method as what if a user constructs the complicated find and then hits the wrong button? Its better to visually grey out the text on the button using conditional formatting and then making it so that the rest of the script only runs in browse mode.
I incorporated the conditional formatting with your first posting. Good Idea, because a user can not
click onto something they can not see.