If you can slide it forward, slowly & carefully, so you can look in the back...? That's awesome that you have tracked him with the flour!
Speaking for myself, I'd be tempted to call an appliance repair guy (& carefully explain the problem, hoping they aren't phobic) if the snake is in there but
out of reach. And I think it would be much safer to cut the power (unplug the frig) for a while while you're poking around back there.