SOLVED: I just had to search harder and find a specific enemy.
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So, maybe i am missing soemthing because i never played the other Bloodborne, so my mistake if i missed a mechanic i didn't khow at this time

But blood echoes puddles began to dissapear after this patch.

i rememer seeing some dying by that first werewolf, but after the second save place with the townpeople with axes, the puddle appears when i die and then dissapears after some time on the death screen.

When i go back to the place the puddle is not there and killing enemies don't give them back.

enemies have a sparkle on them when they have your echos but the puddles dont always seem to drop exactly where you died

If you're familiar with the general Soulsbourne formula then my guess here probably isn't right, but when you say that a puddle disappears on the death screen, you mean the specific one that was caused by the latest death, right? You're not talking about a prior death's puddle? And killing enemies not bringing it back, it's not a case of a specific enemy having the glowing eyes (or however it manifests in the game)?

for what i could see (i tried recording a video on Geforce shadowplay but it was just black), i made myself die to the first enemy after the second save point, the puddle dissapears before going back to the game,  then i returned there there was nothing, killed that first enemy that killed me, and keep going forward, and i still could not recover.
i will try to get a video with obs to explain better, i didn't see anybody having this problem, and i think i am not understranding something.

So i managed to do the video

I see, it just doesn't leave a player character bloodstain at all, it looks like. There's the smoke then nothing. Not sure if another NPC may have absorbed it but it doesn't seem to be the case. Is this consistent, and with the latest version?

I didn't tested in other areas, but in the first version i played and died to the first hunter enemies and i could recover my echoes. 
i am testing now in other areas and is the same thing if i died i lose my echoes in past areas too.

ok i think i discovered what happened and i didn't khew about it.

So i found in another corner of a map a enemy called "lost Hunter, and when i got near them, i don't khow if i pressed the lock on to try to talk or was automaticlly, i got my echoes back!

so it was not the same enemy, it was literally another hunter who saw my stuff and got it!

Thanks Eyesocket and... Vriska for helping me out  (the last one for not thorwing me over a cliff i guess)