If it keeps popping up, you must be in an infinite loop as this specific message just continues the script when you click OK. Try pressing the keyboard short cut for your system to abort the script: (Esc on windows, Command Period on Mac).
This won't work if Allow user abort was used to prevent aborting the script.
Do you have FileMaker Advanced? If so, you can enable the script debugger before opening your file and use the debugger to halt the script.
If not, do you recall a script in the file that changes to a different layout? If so, try creating a small file, establish an external data source reference to this file and run a script in it that uses Perform script to perform this script in the other file to change to a layout that hopefully doesn't have this trigger and script.
You might also be able to use Go TO Related Records from this small utility file to open and switch layouts in the original file though that depends on using Manage | Database | Relationships in the utility file to define a valid relationship to a table in your original file.
I was able to command . out of it today. I was not able to do this yesterday. I then disabled the On Record Load Script Trigger for the Layout for my Find Record Script.