This is never a fun problem to deal with —sorry about the trouble!
I think the key will be understanding what caused the files to go missing. Where were you storing your vault: iCloud Drive or no?
If iCloud Drive is the answer, look in Files→iCloud Drive→Obsidian. What do you see there?
If not, look in Files→On My iPad→Obsidian.
Next, if you didn’t delete the files yourself (either from within Obsidian, within Files, or with some other app that interacts with your iPad’s file system) then the culprit must be some kind of sync service. Were you using Obsidian Sync at all? Do you use Obsidian on other devices at all?