Several really good bowyers have already said that they sand glass. I won't lay claim to being the end all of this conversation but I sand glass on every bow I build to fine tune and tiller. Micrometer in hand while Ido it.
I will plead guilty to having made the same mistake once in my bow building carear. How it happenied I will never know but it did . From that time foreward I swore it would never happen again. I check double check and tripple check just before the bow is mailed. It can happen even in the fine sanding of the finishing process so it has to be constantly checked during the building process.
I have also cut a riser on the wrong side and ended up with a left hand bow . I was building that one for myself./ Stuff just happens.
I would bet that bowyer slows down , just enough to check tiller from now on because that is just embarrassing. Especially on a high end bow. But it does happen. There should be no harm done as long as you get a perfect bow back , just like you like and ordered it. Relax and give the man time to fix it. God Bless you, Steve