Dicentra is a cold hardy perennial once established. If you had planted it out in the garden last fall, it would begin growth and bloom in the cool spring season. The plant you just brought home has been living in a greenhouse. The sudden change to outdoor conditions and overnight freezing temperatures has set it back. The drooping is an indication of cold damage. If the foliage has not perked up, trim it off and wait. If the freeze did not kill the crown of the plant, it should put out new foliage when it gets established in the garden.