If one has now sprouted then you should wait and see what happens. I planted rhizomes for the first time this year, too. I also went through a suspenseful period like you're experiencing. Then, one day one of the centennials sprouted up. The very next day my other two rhizomes sprouted. I went from doubt to having all hops sprouting within 24 hrs!
So, don't give up hope! Perhaps the ground is still a bit cold or something.
Primary 1: Oktoberfest Lager
Primary 2: Apricot Wit
Primary 3: Christmas Warmer MkII
Primary 4: Apfelwein
Bottle conditioning: Vanilla Caramel Creme Ale
Bottle conditioning: Brain Spawn Saison
Bottle conditioning: Hot Shot Rye Red
On Tap 1: Barletariot Cream Ale
On Tap 2: Apfelwein