SNAP! Muffin's been losing hers too! Not found any yet tho... Mind you, they are teeny tiny little things so they have probably been swallowed.
I've noticed she's been having a few bad days recently and I suppose they can be a bit uncomfortable for her at times
So for now, I've stopped her having hard chewy chews and been giving her some cold carrots to munch on. Seems to help a little bit