
Hi Sue,
My cavalier girl Gypsy had this once and it was my fault...I forgot to feed her at night time!

She was exactly as you say your Poppy is, no upset stomach or anything. She sleeps in our room and I was woken by her stomach growling and gurgling, as soon as I woke up she rushed to the door so I thought she had an upset stomach but she just raced outside and started eating grass. She hasn't done it since but I have never forgotten to feed her since, bless her!
I would suggest perhaps adding a little appetiser to your girls breakfast to encourage her to eat it...if it is because she's hungry the problem will hopefully stop :-)