Learn English – Word or phrase for when you’re hungry but nothing sounds good to eat

To stay one's hunger is perfectly acceptable, and not at all uncommon (though it's actually more likely to be "stay your appetite"). Less common, and with less of a "temporarily" sense, would be assuage one's hunger. But I think probably the most common idiomatic usage is...

Here - have a sandwich to stave off your hunger until dinnertime.

...which my mother used to say to me when I was a child. Perhaps this one gains traction by alliteration / association with both stay and starve.

to stave off
to fend off, to ward off (something adverse) _{Merriam-Webster}

(To metaphorically repel / drive away using a stave = staff = stick.)

I have seen the neologism "Ninja'd" for a similar situation applied to Internet forums, on several forums. But this certainly doesn't describe what one may feel in reaction, it only describes the action.

Where I've seen it:

• I've first seen it on Keenspot webcomic discussion forums.
• I see it most notably on the TV Tropes forum (which adds a tendency, on threads dedicated to works containing a ninja character, to use that character's name instead). The administrators recently added a ninja smiley to the forum just for this purpose.