Getting worse now. Made a 4th model and every one disappeared. Shut down the iPad and started it up again. I could now bring up the original 3 models, but when they come up I have to zoom in and out and hunt all over the place to find them. The 4th model I created shows in the Workspace panel, but the only thing I can find is one small curve. The rest seems to be gone, but still shows in the Workspace panel.
Loading it, here is what I get:
After hunting around, I can find this: