What exactly is scallops' "own stock"?
I don't think the author's referring to fluid from the scallops, because on p. 124, she advises buying dry, not wet, scallops.
Refrigerate immediately after purchase, and ideally scallops should be cooked or consumed within one day. Scallops may be poached before freezing in their own stock and stored in the freezer for up to three months. Flash-frozen scallops are also available in grocer's freezer cases.
Totally Scallops: Not Just Another Cookbook (2009) by Judy Eberspraecher. p 136.