Good morning everybody
That's so frustrating Mo. I wish I had some advice for you. Our dog starts digging once in a while. It seems there's something bothering her, but for the life of me I can't figure it out. I like Anansi's idea. It's much better than what we did - took everything away from her and left her with just a blanket, that sometimes is just a dog towel. When she had foam type beds, she and/or the cats were trying to eat the foam pieces. We did find a really good cover, but it was a tent type material so her scratching was absolutely horrible.
Fingernails on chalkboard. She couldn't dig through it but, yeah, she lost that too. We just couldn't take it anymore 
Maybe tons of outside time and equal tons of positive reinforcement?