Break ups are common in couples nowadays but patch ups are also the fact. Through a well written Patch up card, you can express how much you miss that person once he/she is gone from your life. You can choose the one that fits the pre existing relationship and let your beloved know that he/she still means the world for you.
You are incomplete without your sweetheart and desperate to have him/her back in life. Add some romantic anecdotes of the special moments spent together when the relationship was on and see how he/she realizes that you are indispensable for him/her as well.