<human>: A few months ago I was working in a bistro in an interactive science center especially targeted at younger audiences, for example student groups.

One day we had a reservation for a fairly large group of students with special needs. Because of the group's size, we prepared the second story of the bistro for them, which could be accessed by either the stairs of the elevator.
When they arrived I guided them up the stairs to their reserved area. However, one girl with down's syndrome was in a wheelchair so I sent her and her accompanist to the elevator.

Now, when I start my shift and enter the building I need to use the elevator to activate my electronic key, and as I did that morning, the elevator was acting quite strange.
I didn't put much thought into it and carried on with my business.

Approximately 15 minutes after I sent the two in the elevator, I took the stairs to see if everything was alright, the girl was nowhere to be found, to my surprise.
I asked the supervisor whether they had arrived at all - they haven't.
So we shouted down the closed elevator doors only to hear a 
faint "Hello?!"

It took the maintenance staff about 1 hour the get the elevator to be stuck between to stories so I could at least hand them some water.

In the end, both of them were stuck in that elevator for 2.5 to 3 hours and as they got out I apologized as much as I could.

Luckily, no one thought it was my fault and the girl was fine. At least they got the drinks for free.

Summarize the given text in a few sentences.
<bot>: I trapped a girl with down's syndrome in an elevator for over 2.5 hours when all she wanted to do was eat cake.