I think I solved the mystery!! While lying in bed this morning, my youngest DD's cat jumped up on the bed. He's only 7 months old so we haven't declawed him yet. The vet was hesitant. Anyways, he jumped on the bed, twirled, lied down and then began kneading his claws and I could hear him scratch the fabric in my half awake grogginess!! So, I scooted him off the bed and sure enough, there's a little tear in the thread there, just like the other ones! Eeeeeekkkkkkk!