The Cat’s nose

What happened to my cat’s nose?  Saturday morning, my cat came up to me, and her nose was all bloody, the tip was missing, and she had a puncture wound in her face and a scratch.  The cat was INSIDE all night!!  I can not for the life of me figure out what she got into.  She didn’t eat or drink for two days, but I got her to the vet on Monday  morning, and they rehydrated her and gave her some antibiotics.  She’s on the mend and feeling better.   There are two mysteries here:  1) What happened to my cat?  2) Why do pets always get sick on WEEKENDS?