The cyst on her navicular is so big, there's no way it wasn't giving her problems before. Also, with navicular syndrome, it comes on slowly and insidiously. This was sudden, like something wore off.
The only thing I could possibly learn would be if they admitted it and told me what they used. Not sure if I'd feel better after chewing them out, probably not. I'd still be mad.
OK - I can see that.
If your vet doesn't know of 'something' that could be used to mask it now, short of nerving, then probably whatever they did before wouldn't work again.
I probably would end up calling to try to find out, but I can't vouch for it's usefulness. Do they know anything about what you've discovered?