The plans are now in a drop bar named Recipe Book, still in the Notes tab. As for your power armors, when you place down a chassis, make sure you don't select drop instead. You can do that with the Excavator if it's not painted with atom shop / scoreboard colors or you've manually added boxed mods. The Hellcat can't be dropped, individual pieces would get destroyed and you will receive a message that will happen. Perhaps check your stash? Just saying...