I'm not an expert on this, but I'll give it a try. First off, you didn't mention the outs to start, so I'll assume there were no outs.
With the runner on first and a groundball, you can't assume the double play, which means (I think) that you have to make a decision on which runner would have been thrown out had the ball been handled. For example, if the grounder was hit to SS and he booted, you might could assume the out would have been recorded at second....but if the ball was hit to the first baseman and he booted, you probably have to assume the out would have been recorded at 1st.
If you assume the out would have been recorded at 2B, then the run is unearned because that runner should have been out. However, if you assume the out would have been recorded at 1B, then the pickoff would never have happened and the run is earned.
I'll warn you that this is my best guess, and again I'm not an expert. But I think you had to be there to make that judgement call.