TL;DR: Flag it for moderator attention. Start a meta thread if you disagree with the mod team's original decision or their response to your flag.
Your original answer was:
(Stackexchange wants more characters, I think the above is sufficient).
The fact that SE wants more characters is a clear sign that you should be writing more, especially on a site like ours where there usually is no one correct answer and you're expected to back up your answers somehow and at the very least explain why something is a certain way. DCON summarised it well in his comment: "Even though I completely agree with your answer, you need to expand on the why. This answer is incomplete."
You ignored the comments explaining the problems inherent in giving an answer like this. Your one-word answer got flagged and was unanimously deleted. You could have clarified the reasoning behind your answer before that. You can contest a deletion as a result of a review queue but typically there's some expectation that you address the problems the post has first or that the result of the reviews was incorrect. You obviously believed the latter but the community disagreed which is why I decided to uphold the decision of the review queue. I commented the following at the time:
"I think the above is sufficient." I disagree, as does the LQ review queue which unanimously elected to remove this answer as not meeting site standards. Since this hasn't been edited to add further detail I'm upholding the review decision and removing this.
It's only after that that you edited your post but as you saw there's no direct way for you to get your post back on the page. That's why it's useful to consider whether the feedback your post gets is worth acting on or not. And for future reference, adding comments like "For anyone wondering, I spent a lot of time on the above answer." is not the best plan if you want a site community to accept a low-effort one-word answer.
Now what? It's been deleted (with a net rep of -1), undelete says mod did it and I can't undelete. Flagging a mod seems like the wrong thing to do,
Nope, that's the best way to proceed in this situation. Simply flag your answer with some variation of "I edited this answer to improve it and believe the deletion is not / no longer warranted.".
Alternatively you can start a meta question like you've done here or ask people in the chatroom for input. You can also usually find a few moderators in the chat that you can ping, though flagging is more efficient if you want to reach us.
as does posting my revised answer as a new answer.
Yeah, you should usually never do that. If you radically changed a post and the original was very badly received you can consider reposting to "start from scratch" but it's often frowned upon. Never do it if you haven't drastically changed your post.
Based on your edits I've reversed the deletion. I've also edited your post slightly to clean up the formatting. A spoiler tag is available cross-network but probably shouldn't be used for cases like this. If you feel this gives an increased impact to your original one-word answer then you can go ahead and edit it back in though.