The healthstones are conjured items, and will vanish from one's inventory when they log out.
The soulwell animation appears as dropping a stone pyre out of the sky. RP'ers will make jokes about the soulwell nearly clobbering them in the head.
It's possible to invite a warlock into your party/raid to conjure a Soulwell, allow everyone to obtain Healthstones, then replace the warlock with a needed non-DPS type. This is best for when a player in your guild has a warlock alt; it's considered very rude to do this without the warlock's previous consent.