Only on BYC would I find others who not only had a problem with their chicken swallowing something sharp - but cured them! I was working outside the coop and some how a tack fell to the ground. The chickens (who had been in the run eating a tasty combo of yogurt, grapes, and bread) suddenly appeared and it looks like Pip was the "lucky" winner who snatched the prize away from the others.
Hoping she dropped it I did use a large magnet to try to find the tack. No luck. I didn't think of putting the magnet up to her crop. I'll try that right after I post this.
It was a "Blue Tack;" short, fat tacks used in upholstery. Is this toxic? If so I will operate first thing in the morning. Despite living in a rural community we don't have a vet that knows chickens. Or goats.
My thanks to everyone who posted helpful advice. I can always count on BYC!