Missing task, cannot find with any advanced search method.

@Matt5 - what level of account are you on? It sounds like you’ve done virtually all you can do, but if you’re on an enterprise tier, you can try creating a service account (has access to all data, including private data) and calling the search API using that account to see if someone made the task private to themselves somehow.

If you aren’t on enterprise or don’t want to try that, I think your only other option is to work with the Asana support team: