dynamic stamps - won't pull in numbers! MAC OS

After spending an hour on hold and 1.5 hours with a chat rep, he was of NO help.

I have a custom sticker and if I rename the document, I want the sticker to pull in the name of the document with NUMBERS.  So if the doc is named 1, the sticker will pull in the 1.  it does not work. it is the Only field that doesn't work!  Someone Puh.leeeeeeze help me ASAP!  Thank you!

Here is the javascript that is "supposed" to work but doesn't. Keep in mind this stamp works on WINDOWS and Adobe says on their own website that stamping works on both platforms...

Here is the script:  

event.value = event.source.source.documentFileName;