Replying to Pre-Employment Drug Test

So I have a bit of a concern that I thought I would ask NS about...

I have a pre-employment drug screening tomorrow.  A few summers ago I broke my back and slipped some discs.  The back pain still hurts me today.  They never really gave me anything for my back, but my mom had an old scrip for Vicodin which she gave me.  When my back is really hurting me to the point where I can't really work I will occasionally take a Vicodin.

 They are 5mg/500mg pills, I took one yesterday around 3pm.  It was the first time I had taken one in a couple of weeks so I am in no way a regular user.  My test is tomorrow morning at 9 am.  Think it will show up?