I know the heartache. Try to not let a shop hold you back from continuing to scheduling other shops.
In other words, when you have an application in for a shop, just mark it as 'pending' in your calendar and continue to schedule other shops, as you desire. Obviously, if you haven't heard back and would like a shop in a different area in its place, I'd just cancel the application for that initial shop I was waiting for and then reschedule to another date and wait again.
If I end up not getting a shop? No sweat. If it's a shop I really desired, sometimes I follow up with the scheduler / MSC contact directly and inquire about their selection process, if I'm not familiar with it.
Shopping the Greater Denver Area, Colorado Springs and in-between in Colorado. 33 year old male and willing to travel!