Right. Moraines around now are mostly from 12,000 or so years ago. But they are examples.
Moraine from 250+ million years ago would almost all be long-buried by plate shifts and extended glaciation periods since then. That’s why they’re ‘missing’.
You would be able to find them in the bowels of the Cambrian ocean. It would be difficult to hide thousands of feet of rounded cobble-sized stones. They are not preserved anywhere. But it makes for a good bedtime story.