does anyone know a seed to get a missing poster Afterbirth +

[LawnChair]

Im trying to get the lost but i cant find a missing poster

[Part-Time Prick]

A seed won't help you, ya dumbass. XD
The unlock won't count. To be honest, it's kind of easier to unlock The Lost in Rebirth due to the fact that there's no RNG involved.. Well, there is, but there's a few broken seeds that let you get where you need to with the characters.
The only proper run is the Azazel run you gotta do to Sheol to get Satan to kill you. That's it.

Just pray to RNG for now, you'll find it eventually. Sorry for the whole "Pre AB" talk, just a poor person's perspective on the matter.

[LSDBunny]

Did you unlock the poster?

The best way to find trinkets is to search for Mom's Box (shop item), which spawns a random trinket every time you use it.
Another way is to look for a fortune teller. Those are often in super secret rooms and will sometimes appear in arcades. They also can be spawned by the Wheel of Fortune card.

[Ov Å̪e̞oη̣s]

seeds will NOT count towards unlocking lost, can either mums box, use eden tokens or just get other things done till you find.

i got mine with about 34 eden tokens.

[LawnChair]

XD i didnt know that seeds didnt work

[Footsome]

Seeds do work you just don’t get achievements.

[Part-Time Prick]

Reee, necro.

[Squeezz]

You can also use console if you are so desperate to get it.

[Marcore]

I did it this way (afterbird):
Play as Eden and restart until you get mom's box (you have to have enough tokens, and yes you can unlock The lost with any craracter, not only Isaac).
Now all you have to do is to get the missing poster using the mom's box and kill yourself in the sacrifice room, i just did it this way yesterday.