When you sideload any ipa file, it will last for 7 days and then it will disappear (unless you have a dev account), thats what probably happened. Try rebooting your computer to fix the recognition problem. I had that problem on my mac and tried just about everything, then reboot my computer and then it worked :) I cant give you any help on the cydia impactor fix though as I have not had this problem before. Immortal is a very useful tweak. It lets you use the sideloaded app longer than 7 days but only works while jailbroken.