Considering Anna was being held for murder and they would have other patients being held for similar crimes, they would have had to have had a lot more than CCTV, several locked doors, guards and they would have to check ID.
There is no way that Will, would have been able to get to Anna just with Ash's card, he was also wearing a fluorescent vest, he was very noticeable and people would have remembered him (and as he has been seen visiting Anna in a wheelchair, but was seen walking that day, it is even more memorable) and backed up Patrick's statement to the police about the guy.
I bet they will just ignore it all though.
