Can you feel the string in the crop? I've had to open a crop once. It's not pretty and not something I would want to do on a chick. She'll slowly starve this way, it would be best to put her down.
On the dogs eating things that impact the intestines... my mom and dad's doberman had a fetish for my mom's nylons. She ate one once, to the tune of $1800 of surgery. She did it again a few months later, pulled open the drawer of the dresser to get the nylons out. Stupid dog and her fetish. My dad said that's it, she either passes the nylons or she doesn't, he was so mad at that dog! She did, and that's a whole other story in itself in pulling out that long strand of nylon.
Believe it or not, she lived for 9 yrs after that to the old age of 14, probably because my mom starting putting her nylons on the top shelf of the closet. Just trying to enlighten your situation. I hope your chick pulls through, but chances are it's caused a blockage. Last ditch effort would be a lot of mineral oil to try to push it through.
On the dogs eating things that impact the intestines... my mom and dad's doberman had a fetish for my mom's nylons. She ate one once, to the tune of $1800 of surgery. She did it again a few months later, pulled open the drawer of the dresser to get the nylons out. Stupid dog and her fetish. My dad said that's it, she either passes the nylons or she doesn't, he was so mad at that dog! She did, and that's a whole other story in itself in pulling out that long strand of nylon.