1. Change your record with the hospital immediately. If you're already discharged then write them a letter. If you're in the US, you have a legal right to write an addendum to your medical record. Do it. You never know when you might need to be admitted again.
2. The elder may very well have found you because you listed yourself as a jw (by your failure to object when your mom told the staff your religion). HIPAA allows directory info to be given unless you specify no info is to be given to anyone. Clergy of all sorts come in to the main desk and the hospital and pick up the lists of their flock to visit. (TIP: If you don't want clergy to visit, have your record changed to "declined to state religious preference".)
3. CC all your providers on your letter about your religious status. State you accept blood if necessary (if that's what you want).
By not objecting, you have potentially put yourself in danger.