Grand arena

Well there's quite a lot to unpack here.

From the description, you clearly didn't win, you lost the battle.  You were then given the choice of uploading or having a clean (no dmg or preload) battle.  You weren't there in the short window you're given to make that choice.  If you were away for just 2 minutes as you wrote (from thinking the battle was won, putting it on auto and for the battle being expired)...hmm that's an extremely short window.  That really wouldn't happen often.  I mean...at the very least you must have been really pushed for time when you put it on auto.

When they coded it to be like this, I don't think they had an easy time of it.  The original PvP coding made it incredibly difficult for them to give us the choice (submitting or forfeiting), as I understand it.

If they were to give us an endless window to upload the damage, then they'd have to code TW differently.  You can't leave battles hanging in TW indefinitely.  As it is, with all the other issues in the game, it's really not worth it.  Especially, as they had issues coding the submit/forfeit in the first place.

What we have now is much better than we had before.  We use to have to put the game into aeroplane mode so that we didn't preload.  Having to use an outside the game function on your phone/pad/computey thing is far from ideal.

Obviously, real life happens, but if you've walked away and left a PvP battle (for whatever reason) then that's user error.  We've all (well a lot of us) have done it.  Put it on auto as it's quicker and totally forgotten about it, to come back and the match has been erased.

Take it as a learning experience and try not to walk away from a PvP match - you never know when you'll be needed.