If the side that stuck to the sleeve was covered in ink, then the ink probably had not cured right. If its made using a home printer, then that is probably why, as that kind of ink needs to sit out and cure, exposed to air for a good month sometimes. You can try getting a sponge brush and adding a coat of Future to the next one, and let it cure/dry in the open air for a few days before sticking it in the case. Other then that all I can recommend is having it laminated, or makeshift doing so yourself with clear packing tape, applying it carefully and cutting it to fit.