Thanks everyone for your concern. Unfortunately, I have had no luck in finding Rosebud. However, I did contact ne of the pet psychics, Liesl, and she did a reading which was very informative. She asked me why my kitty was so mad, and I told her that she was unhappy with our other cat, Tanny, a big orange guy who is a bully. Then, Liesl told me that she thinks Tanny had attacked and bitten Rosebud and that she had run away to the woods to get away from him.
This really rings true, since they were both outside on the last night I saw Rosebud, and Tanny came inside when I opened the door. Rosebud was nowhere to be seen. It also explains why she didn't come home the next day, which was very unusual. Liesl saw her in the woods near a creek and very weak, but still alive. This also rang true, as we have a lot of woods and a creek that runs in back of the subdivision. I spent a long time the last few days walking up and down the creek area calling for her as loudly as I could (upsetting all the neighborhood dogs terribly), but there is still no sign of her.
Even though she's still missing, I feel that I gained some insight into what happened. Tanny has been a problem for a long time and now I know that I should have taken more care that Rosebud was protected. If I ever get her back, I may have to find him a new home, or let him be an outside cat. Liesl said that part of the problem was that he was bored.
I am also planning to call the number that Seamus gave me. I hope it's not inappropriate to contact more than one psychic. I didn't say a word to my family about this, since they would think I was a fool, but I strongly suspect that these people really do have a gift. It's a shame that the term "pet psychic" is met with so much derision.