Are Yoshino usually grafted? We have one at work, but I have no idea if it's grafted or not.

It's a big 'un.

The Weeping Higan Cherry, Prunus subhirtella, var. pendula or sometimes listed as a cultivar, 'Pendula' is most often propagated by bud grafting, but there are a couple of online companies that offer cutting grown trees. They are LazyS's Farm & PendulousPlants.com

It used to be quite common to find cutting grown trees in the Atlanta area. Mine came from a local nursery, either Pike's or Green's (don't remember which one). more than 30 years ago. It has a Japanese cultivar name, which has been lost to history, as someone on a tour of the garden several years ago, took the copper name tag with them.
I don't bother to tag trees and shrubs anymore, since the metal tags seem to disappear with irritating frequency.

Hope you find one, as they are are a beautiful small tree all year, especially during bloom time in the spring.
Rb