Storing Dicentra Rhizomes?

These Dicentra Rhizomes were cheap but have no directions for planting. From what I can gather, they should go in about 6" deep laying on their sides? The problem is that the bed for them isn't ready (too busy repotting babies) so I'm not sure what to do with them. Is there good way to keep them, or should I plant them where they are to go, but a little shallow so they don't get buried too deeply by the compost, cardboard, and mulch when I get them put down? "Regular" perennials I would just keep in a pot til they're big enough to go out; since they're so big, I guess I could plant them in window boxes for now if that would work.

Any help appreciated.

Is it to late for any help?

They're planted in a window box, haven't sprouted yet.

Gosh, I thought dicentra was indestructible! If you have had them in soil and have kept them slightly moist I should think they'd have sprouted. Dicentra is almost impossible to kill.
Have you checked the root area for activity? Are you sure the tops are not showing life?
Most important of all, since they were "cheap", is the rhizome plump and prospering, or were you sold old, dried up stock?
Try contacting the vendor about this.