There's an almost unlimited number of ways that something can go wrong. Sometimes, BOINC thinks the task has died even after it's successfully uploaded a correct result to the server. The task is marked as an error, no credit is given, and the project sends out a replacement task to duplicate a perfectly good, yet discarded, result.
That sucks for both the user and the project. And that's what happened to you.
A few years ago JimB created a process that looks for such tasks and resurrects them. That's why you saw the task change state. It's as if nothing ever went wrong. When a wingman task completes, your task will validate just like any other task, and assuming the result is correct you'll get credit.
Unfortunately, the resurrection doesn't prevent an extra task from being sent out, so there's now three tasks -- yours, plus two that are in progress. When either of those two complete, yours should be validated.
My lucky number is 75898524288+1