Well, this is a sh*tshow. This isn't the first rally where Trump's lack of staff and event management punish his own supporters. Via Daily Kos:

The rally wasn’t held at the same venue as the famous music festival that draws a quarter million people over two weekends to the southern California desert. Trump clearly was banking on the famous name for positive association, though he held his rally on a private ranch. Everyone was required to take shuttle buses, no one was allowed to either drive or car-share to the venue. 

“The Trump campaign said Friday that all guests arrive by shuttle bus and people will not be allowed to walk or take rideshare vehicles to the venue, an isolated ranch,” reported the Desert Sun, a local newspaper. “Instead, starting at 6 a.m., attendees can park at three designated locations and be shuttled to and from the venue. At the end of the event, they'll have to make sure they board a bus headed for the right lot.”

While Trump claimed 100,000 attended the rally, the event was only permitted to have up to 15,000 people. 

So the Trump campaign holds a rally at a location that is only accessible via shuttle. They move up to 15,000 people into the venue. Their own guidance instructs attendees to board a bus back to their parking lots. 

And then those buses didn’t show up after the event. 

Trump doesn't have a campaign staff beyond his daughter-in-law Lara and Stephen Miller. All of the grunt work required to hold an event like this? It is too expensive for the grifter Trump, who likely has no thought for actual people needing a ride back to their cars.