My mother never found the pills, she found the receipt in the Trash. So theoretically speaking, anyone who finds a receipt for my medication can pose as my mother and verify my medication/ dosage with my psychiatrist?

There isn't much use in "theoretically speaking." Your confidential information was breached (discovered) by your mother in your home as a consequence of your conduct. No one posed as your mother. Your mother called the physician to complain and protest, not to verify the contents of the trash in her home. You are experiencing misdirected anger.