The reason there might be an X next to your Snapchat friend’s name is that they removed your from their friends list or blocked you, or you removed them from your friends list. To get rid of this X you should first check if they are on your friends list. If they are not you should add them to your friends list and the X should go away. If they are on your friends list you should check if you are on the their friends list. If you are not you can politely ask to be added to their friends list. If done correctly that gray X should be gone.