Darn, I hate that. My feed store is always out of the pellets but always has the crumbles. I don't ever need the crumbles because I can make a mash for everyone with the pellets if I need to. It's annoying. (I know I shouldn't complain, at least I can get the crumbles...

)
Anyways, that's a bummer. Unfortunately it seems (I'm totally over-generalizing here and somewhat resemble my generalizations) that a lot of the feed store places come with a somewhat small-town mentality. Hopefully you can strike up a conversation with a manager/owner or such and help dissolve any possible barriers that might be keeping them from hiring you. I know when I was an employer, the people that kept coming back (almost annoyingly) and talking to me and hanging out, usually got a job. It's not an easy thing to do, though, especially if you're somewhat introverted.
Best of luck! They could just be slow to process everything as well, so sometimes it just takes awhile. Following up never hurts, though! I hope you can acquire some feed soon, too!