Don’t know if the post messed up the smart quotes but that could be where the problem is. Replace all the smart quotes with standard quotes and see if that helps:
"SQUARE "+superdatepattern(supernow(),"Month ddnth, yyyy at ","hh:mm am/pm")+".txt"
The colon in your time is being converted to a slash, and that causes it to be mistaken for a folder separator in the path.
This looks like a bug to me. It’s not going to convert a valid HFS path to a valid UNIX path because an HFS path begins with the volume name, and a UNIX path does not.
In the Finder the file name appears as 1/20 PM. ls in Terminal shows it as 1:20 PM. When I dragged its icon into a Panorama procedure window, its name in the path that was written was 1:20 PM. However, fileload( can’t load a file with that name.