Need more info.... What did you do after it was knocked over? Is the plant still connected to the root mass? What happened with the soil....how is it now? Have you watered? Is it wet, dry, moist now? Did you change it's location? I will say this- BNF are sensitive to touch. The leaves will bruise if you brush up against it. While it doesn't require the humidity of some of it's cousins, it does appreciate it. They do best with moderate to bright light. They don't like it when you get water in their crowns! Rot, rot, rot and more rot. LOL

If it sits on the grass to water and drain then sneaky snails could have snuck in within an hour. And caterpillars are laid as eggs on plants by flying insect adults. It does look like damage from one of these munchers though. Kind of a relief, I believe. Do you have lettuce or even potatoes? You can lay them on top of the media to try to attract snails then squish and flush them. Also, if you repotted it and havent had it long its entirely possible there were snail eggs on the roots and they hatched after you repotted. Some people spray roots with hydrogen peroxide to kill snails and their eggs but I'm not sure how a fern would handle such treatment.

In a planter without a drainage hole " a layer of porous lava rocks lining the bottom" DOES NOT ensure proper drainage. Only porous soil and drainage holes ensure proper drainage. You need to get a pot with drainage holes.

Remember they're epiphytes, so don't have the soil too high up around them.