Sheesh, they're bold, aren't they? Don't they know those plants are *pricey*???
I have never grown Epis, and so if anyone with specific experience chimes in, that would be much better. My advice is general for succulents.
First, give the "cutting" (or biting, as it were) a chance to dry where it was severed. 24-48 hours. Stick it in your potting medium - do not water, but lightly mist it every few days. Someone said once that if there's no roots, there's no way to absorb the water, so it's a sure fire way to get them (succulents) to rot.
My question about epis is can they root from the middle of leaf like that, or do they need a some sort of growth plate from which to sprout roots?