So today I opened up a file I had not worked in a while, and found only 2 of the 4 masters I had. I thought I must have somehow deleted them by mistake, but the thing is, instances are being generated from the missing masters!
I had 4 masters: thin–>bold and thin italic–>bold italic The italic masters are missing, both from the tabs on top of the font window, and from the masters pane. But if I select “view all interpolations” or see the instances window, the italics are there, I just can’t access/edit them. They also get generated when I export the font.
Font edit window: