Standby for flight booked w/VS points

I have travel/jet lag brain so forgive me if this is a stupid question. I booked a short positioning flight home for this week on DL using my Virgin points. I'm realizing that there's another DL flight that will get me home sooner as long as my international flight gets me to DTW on time.

Delta app won't let me change it and neither will VS. Called VS and they said they don't see award availability on the alternate flight so there's nothing they can do. Fair.

Will I be able to go standby on the earlier flight if I ask at the airport? If so, is this a normal thing or something the GA will do if they feel like being nice to me? Or is my only option to cancel what I have and pay too much $ to rebook?

Thanks!!