EMT's and paramedics will NOT check your wallet at the scene of an incident. They are careful to protect the privite property of a patient from a legal and ethical standpoint. We are trained to check for a Medalert bracelet or necklace. Eventually the hospital staff may check a wallet for ID or a contact for an unconscious patient, but probably only after treatment.
If blood is required, the treatment facility will always type and crossmatch, no matter what a card or tag indicates.

"There is nothing so frightening as ignorance in action."