Not a clue

Tickets to the event had been sold out since May.
Somehow, Holly scored a pair, and asked her friend Tina to come along.
“What is it for?” asked Tina.
“The best show ever!” said Holly .
“But what is it?” Tina asked.
Holly didn’t know.
She looked at the tickets, but they just had the date, the time, and the venue on them.
She couldn’t remember how she got them.
Even her credit card statement didn’t give a clue.
“We’ll go and find out,” Holly said.
When the day came, they got out of the Uber and walked into the door.