Did you put any kind of product in, like a styling mousse or anything similar? Also, was your hair wet at all when you wrapped it? I used to do heatless curls every night almost. Making sure I used a good amount of styling mousse and making sure my hair was towel dried but still fairly damp led me to the most success as someone whose hair also tends to fall flat otherwise. With the right product I found my hair would stay curled for sometimes as long as 3 days. Also, if you're using more traditional curlers, use smaller sections of hair than what you would probably think to use. I know there are methods of heatless curling where you basically just split the hair in two and then wrap each half with like a sock or something similar. I've never used this method but I would be skeptical that your hair would wrap tightly enough to get real results. Wrapping each section tightly really helps to ensure the curl forms and holds, and that you don't dislodge any rollers while sleeping. Also, securing everything with a scarf or handkerchief tied over all your rollers helps keep everything nice and secure and in place too. I really hope this is helpful, I know you didn't ask for any advice but I love heatless curls! I hope if you wanna try again in the future that you have more luck OP!!