There are some exceptions, including various forms of unlawful discrimination, which would warrant a convo with an employment attorney.
There's also the possibility of pro-rata equity (or cash) payout if you happened to be between two vesting periods. If they didn't give this to you, you might request it before signing your separation agreement, which is one final moment you have a little bit of leverage.
You should just move on, in my opinion.
Pretty crappy way to do it, I’d love to hear if others have similar experiences