For those who don't know, the reason that they did this to me is because

I am young and healthy, and did not get any additional medical treatment the whole year (other than a covered checkup and a free flu shot), so I had a deductible that I never touched. (I have to spend $2500 before insurance starts covering extra, and was in the hospital because of a body fluke.)

She did not think that I could afford that $2500 and was afraid that I would skip out on the bill or be unable to pay the hospital anything afterwards, so she asked for a deposit before I could leave.