Most Helpful Guy
Looks like He still cares about you, but he possibly has a new relationship that's not working out the way he hoped and your signing his card gives him hope that you might still be available for him, but he doesn't want to push his luck. If you still care about him and you don't buy his reason for breaking up with you, then you need to be honest with him and ask him the real reason for the break up. If he's stressed right now, give it a couple of weeks for him to settle down, but keep in touch, send him a short text, ask how he's doing. His responses might give you a clue if he has moved on and doesn't want you to bother him.
Most Helpful Girl
NOPE. DO NOT. DON'T YOU DARE. PUT THAT PHONE DOWN!!
When someone dumps you, you have go to gather your dignity and keep it moving. Don't beg or plead. Don't try to get their attention or remind them how much your worth. You should never have to try to "sell" your worth to a loved one. If they can't recognize all the exquisite divinity that comes along with your flaws, then they don't deserve your time and energy.
Don't hold onto the hope that you will get back together. Don't wait around, making yourself accessible, despite the fact that he gave up on you. HE LEFT YOU. He disposed of the relationship as if his feelings are all that matter. Delete and block him from everywhere and do not speak to him for one month MINIMUM, ignoring his calls and texts. Don't be that clingy, desperate, pitiful girl who looks like a poor, little, abandoned puppy from an ASPCA commercial :/ Not a good look.