I've experienced the "dissappearing FA" from F as well. Several of my trips have me heading to PHL and DCA and each time after meal service "poof" they're gone!

On one recent trip, after the FA came to check on folks, he passed the snack basket around and announced that if we wanted more the basket was in the galley! And he left again!

It only took a few of those in Y to discover they could waltz into the F cabin and get stuff free! Forget about ordering from Red!