Missed win - help

Hi guys was just analysing a blitz game and it says I had a missed win here but I can't seem to figure it out. Any help would be appreciated. 

Sorry if this is the incorrect forum, first post here!

Thanks 

Here is the position in a pgn diagram (the op has the Black pieces) to make it easier for everyone

This ...h5 move is a nice one, but I wouldn't be so harsh as to say it is a "missed win." The computer is usually spot on, but we as human players must understand how computers evaluate and then interpret their evaluation as we see fit. 

From a human perspective, the ...h5 idea is positional in nature and not so easy to find. The idea with ...h5 is exploiting White's pawn structure around their King - especially the g3 pawn jutting out. This threatens ...h4 and Black hops to either rip open lines on the enemy King, or make use of the Rook on the h-file. In fact, the pawn storm pawn push here is thematic in many positions - including (but not limited to) positions where each player castles on opposite sides of the board.

Judging the position as is (not looking at prior improvements such as piece development or castling early on), ...e5 is logical because you are going for a pawn break in the center. However, this may be premature because your King is still in the center of the board right now (opening up the center with your King there is dangerous). Black advanced pawns on both flanks, so it isn't so clear as to which way Black can safely castle, but your King safety is partly why ...e5 is seen as a mistake by Stockfish. A vague plan for Black would probably to play ...h5-h4 if allowed (for reasoning above) and to prepare O-O-O. Black's Queenside structure isn't ideal for castling by any means, but it may be safer than leaving the King in the center.

...h5 is a tough idea to find here if this motif was new for you. Probably the biggest takeaway, in my opinion, would be to castle early in the game, so your King isn't in the center like it is here. When your King isn't safe, then many good-looking ideas aren't so safe.

The above analysis kind of misses the boat imho.  Black is up a piece (which wasn't mentioned) but has absolutely no development (which also wasn't mentioned).  If black plays e5, the position is definitely opening up, and after white plays e4, all of his pieces come alive providing some compensation.  Black is still winning, but could potentially get in trouble given that the advanced pawns around the king create weaknesses.  Give the engine a little longer, and h5 drops down, with e6 and f5 being preferred.  F5 prevents e4 and also allows development of the knight.  E6 seems more natural to me though, and the engine also likes it.  What e6 does is allow development of the knight, and reinforce e5 so that e4 is not such a big deal.  H5 is a weird looking computery move that I would just ignore; it is not truly a "missed win" but simply one of several better moves than what you played, and perhaps the least natural one.  

haha thanks for the honesty. I gave the position only a glance (why I also posted a diagram [via FEN]), so others could have a look. I still think the ...h5 motif the computer likes (albeit may be temporary) is aimed at White's pawn structure, but I am glad you gave this position more consideration than I have. 

@ArtNJ gives lots of good quality advice in the forums @Knightmare14, listen to this post over mine

Sorry if my post wasn't tactful.  That happens when I post when I have insomnia lol!  I don't think you are wrong per se in extolling h5s general characteristics, its just that being up a full piece with no development and lots of potential weaknesses are the elephants in the room you know?  With those issues being what they are, I'm not entirely sure why h5 is initially considered one of the top choices -- maybe preventing qh5, which could be an issue in couple moves, is a factor?  Sort of a weird way of closing a weakness.  

How does 12..f5 prevent e4? Seems like white can still play 13. e4.

Your right james, that was sloppy of me.  I don't really know why the engine is rating f5 highly I suppose.  It recommends f5, e4, e6, which looks fine and I suppose results in black having more room to develop.  

As far as I know, a missed win doesn't mean that you have missed checkmate, but that you have missed to win a piece or improve position (more experienced players please right me if I am wrong).

Whatever it means, it just doesn't fit here.  Black is up a full piece and there are several moves that keep him firmly on the path to winning; black just picked a bad move, that took him off the path.  

Well, computer sees something that we cannot think of. Sometimes it shows me a missed mate. And when I look at it it was a 20 moves mate. There was something that is better to be played, but it is definitely a lot of moves ahead. When you see something like that, do not worry about it.

Your good. Reminds me of Capt. Binghamton from McHale's Navy when he was trying to be nicer:

"It's as my grandmother used to say, no offense intended, no offense taken."