If your rabbit hasn't been eating much for more than 24 hrs, then yes there is a problem and you need to find a more experienced rabbit vet who knows that when rabbits don't eat(or hardly at all) for more than 24 hours it's an emergency. I your rabbit still isn't eating much she likely has developed GI stasis, which can be fatal if not corrected.
http://www.bio.miami.edu/hare/ileus.html
Rabbits don't just stop eating or drastically reduce their eating amounts for no reason. It's either from a serious stomach upset, bowel obstruction, dental problems, or some other illness/injury that is causing pain. And if it isn't treated correctly, rabbits can end up dying from not eating because their digestive systems start to shut down. In the very least your vet should have prescribed a gut motility med like metoclopramide, a pain med like meloxicam, a syringe feeding mix to feed your rabbit every 4 hours, and possibly even sub q fluids given by the vet.
If your rabbit is trying to eat sawdust and bedding, it's likely because she is craving fiber to help get her digestive system moving. If you don't free feed her grass hay like timothy hay, I would do that immediately and see if she'll start eating the hay on her own. I would also offer leafy herbs and greens like cilantro, parsley, and green/red leaf or romaine lettuce if none of them are known to cause digestive upset for your rabbit. I would do this immediately as she needs to get eating right away. She's already gone far too long without enough food. Also offer clean fresh water in a dish.
I would also try and get her seen by an experienced rabbit vet today, immediately as an emergency. The vet needs to check her teeth to make sure they aren't the cause of the lack of appetite. The vet also needs to rule out a complete bowel obstruction and bloat. If your bun is dehydrated the vet should give sub q fluids. If your bun is not eating from a digestive upset, the meds usually prescribed are a gut motility med, pain meds, and syringe feeding food mix, at the very least, to be given over the next several days til your bun recovers.
Check this list for possible rabbit vets near you.
https://rabbit.org/vet-listings/
If you are in the UK I'm not sure what you will have for out of hours for rabbits, but for normal hours tomorrow you have some very good rabbit vets, hopefully one near you.
https://www.harcourt-brown.co.uk/
https://rabbitwelfare.co.uk/rabbit-care-advice/rabbit-friendly-vets/rabbit-friendly-vet-list/
