I had a dream once that I had been cast in the title role in Hamilton, which is a bad idea for a few reasons, not the least of which is that I'm white. But I went out on stage anyway. I performed so poorly that I was replaced mid-performance, but nobody had told me that so there were two Hamiltons for a little bit, performing in unison. I eventually figured it out and left the stage.
Even if you miss Groban- his understudy, Scott Stangland, performed the role in Boston and is wonderful in it. And on his scheduled off days over the summer (I believe 10 performances over the course of May/June) Dave Molloy, the composer, will be performing!