Should I put this on the motion to show cause with the other violations?
Of course you should. Your ex was required to disclose ALL assets, not just what he felt like sharing.

Or will the judge think I am being petty?
That's going to depend on the judge and the amount in question, but the judges of my acquaintance don't look kindly upon trying to pull a fast one on the courts, even if it's only a dollar.

Serious people, them.
Can I ask for my half?
Yes, and you should.