I’m sorry you’re going through this. Sadly many places that board animals (even vets) can be very abusive to the animals. I shadowed at vets where the techs were so mean to them and I was totally freaked out. Many places often don’t spend time with the animals, they just feed them and leave, due to having to care for many animals. Are the buns both fixed? Do you know if the people there knew about bunnies at all, like with general health issues or just in general? Just so it can take a worry off of you not having to freak out over an accidental litter.
You can always talk to the place and ask them exactly what they did to the buns everyday since they are not acting normal. If a bunny doesn’t have interactions for a couple of days, they can become distant. I would suggest to sit on the floor with each one and do the bonding steps with them all over again. Let them sniff you and see that you’re not a threat and even have some treats and let them eat them from your hand.

Maybe they had a bad employee who was mean to them and so they got scared being there without you. I hope she will come around back to how she was before. I know how it is to break a bunny of being scared of you and then something happens and you have to start back over.

And see if the friend can go to your place to check on them since the buns will be more comfortable in their house than someone else’s.

God you could sue for something like this especially since putting two unbonded bunnies together is very often fatal. I wish you the best of luck with rebonding with your buns I’m doing it too, just remember to not get too frustrated!