Do you have garlic and/or ginger? If so, you're set with just soy and a splash of steak sauce. I rarely thicken my stir fry sauce with cornstarch. I like just enough sauce to coat my stir fry. Just a splash of steak sauce though. Taste as you go and add that last. In my head, I'm comparing steak sauce to Hoisin.

I use plain soy sauce on so many things, just by itself. It has a ton of flavor so, to me, that's all I need.

How did it go? I often just use a teriyaki style sauce (soy sauce ( substitute), wine/rice wine/hard cider, honey and vinegar). I never thought to put thickener in it and mine tastes yummy.

The steak sauce sounds like a good addition.