Use other methods of communication, find them directly or write them a letter. It could be that they've lost there phone rather than they're giving you the cold shoulder.

Just piss on their cat.

That should have been "but DON't tell them what it is" ;)

Simple, phone and leave a message, tell them the craziest thing has just happened to you but tell them what it is. You can say you'll call them back at such and such time. Recall, then if there is still no answer, leave your number and tell them to get in touch. If they don't...move on. By the way if nothing crazy has happened to you, when they ask; either ignore the question by asking a question of your own or just say oh...it was nothing, then start a new topic. Or make up a crazy story, if it's funny, it'll do no harm.

keep ringing them until their freakin fone is dead

Oh don`t worrry about it, there are plenty of other nice people out ther

masterbate

consider suicide?

just forget about. if someone is sincere then no matter how his will take the initiative to call back.

If important confront them personally, If not, forget it!