Isn't it funny that my office is on the hunt for the mysterious fork thief but they don't know that it is me.
Are you trying to mess with the office by doing this?
Of course. They can't solve this mystery. They think it's someone else.
Stealing always harms the character of the perpetrator and is completely unethical. Talk to your coworkers and try to make amends for your immoral behavior.
But I'm the person that's doing it. They'll never be able to prove it's me. Who would suspect their own colleague of stealing utensils?
Stealing cutlery from your office is pretty immoral. While you may think it is funny to mess with your coworkers, i doubt it is funny to them or your management.