Today I needed to open a 4 year old photoshop document, and got the "font substitution is about to occur" message.

OK, so the font was missing. I have gone through the required process of various search engines and type foundries, without any luck.

Photoshop insists that the font is called "stem", but so far I have not been able to find a single font with this name, perhaps it has mistaken the name?

Anyway here is a sample image: