Where did Ruth get Billy's red dress from?

They didn't explain why his dress was at the hospital unless when he was brought in he was wearing it, but they never said that. This film was a tear-jerker. Really sad.

EDIT: I was just watching a story about Ruth Coker Burks on CBS Sunday Morning and apparently Billy in the film is a composite character. She called the man she first met in the hospital 'Jimmy', but I don't think that was his real name. Billy was someone she was friends with later who died of AIDS and he was the one that gave her his red dress.