Hi Hinda! Although I've never heard of it being done with just leaves (I've always used a cut branch), I always put them in water and eventually they grow roots. Some types take longer to root than others. I think that the outdoor ivy that I did took about a month before it started to root, while an indoor one i did took about 2 weeks to start.
As long as it's green and looking OK, you're fine. The shriveled one I wouldn't bother fussing with-it probably shriveled because it had no roots-you could try sticking it in water to see what happens.
As far as I know (which isn't a whole lot), ivy should not be kept in water any longer than necessary. After a while the roots get kinda yucky. I've potted up several cuttings and they all did fine-they may go into "shock" and stop growing
for a bit. And sometimes, if the roots didn't develop well, it may last for a little while and then shrivel, but overall, it's pretty easy. Good luck and keep us posted!