Chris Tann does this link remind you of the account you're referring to? It's in a coffee shop, not a hospital, but the "magic" sounds the same.
This is a prank which has gone viral recently. Your account sounds like the genesis of an urban myth based on it. If you read some of the articles on Snopes.com you can see how these sort of stories start and then change.
This is just my theory, but changing the location to a hospital rather than a coffee shop (more dead people \ angry spirits in a hospital) gives the story "spirity" credentials and changing the man into a child ups the emotional hookyness.