Police hate taking reports in parking lots because its "not a public way(road)" which makes it much more difficult for them. Some departments are easier to work with than others, but unless there is security footage there's really nothing they could have done. (And even with security footage it is hard because many cameras are so low quality that you can't tell what's what anyhow.) I hope everything works out for you though! Sorry I can't be of any real help, just wanted to explain what the cops are dealing with.