I'm positive that you are right. There can be a mass, and there will be. Victims whose body is never recovered have masses said.
Michael has won no victory here.
He can probably sue to get an injunction to stop a mass for Terri, and he will just to spite the Schindlers. He hates them for being Terri's parents, and he may have hated her because she was so unwise as to ask for a divorce in his private presence.