Yeah, it sucks. It's basically the same as in business life, where it's called a hostile takeover.
Sometimes a band even holds a meeting with a lawyer, to have legal referrals, and kicks out the founding member while keeping all the songs.
This happened a few years ago to Liv Espenes from Liv's Eyes.
I'm very sorry for your loss, dude. At least the band hadn't yet developed songs
you had written..
Maybe, when starting a band, one needs to start with defining legal documents, then place adds in magazines and the net, hold official interviews/tests, have members sign the legal documents just like when signing contract to a job.
If the band then kicks out the founder, he/she can do the court to claim damages and legal rights to songs&lyrics.
One topic I need to bring up: It sounds like all the other members had agreed to carry on without you.
Which necessitates the question if you acted overly controlling?
My feeling is that you never indicate such behavior in here..
Best of luck with the next band efforts.