I think you're misunderstanding. It's absolutely possible to seize rockets, or model 3s, etc. That part isn't silly at all.
The only question is regarding which entity is liable. If a judgement were entered against SpaceX, for example, then absolutely rockets and real property owned by SpaceX can be directly seized.
Without looking, I'm certain there are at least a few companies owned by Musk which could have their assets taken directly.