Beat Satan with The Lost, unlocked achievement but not "The Mind". Is it bugged?

I beat Satan with The Lost but didn't get the item, only the achievement. Why did this happen? I am wondering if I have to actually win the run (beat The Lamb) in order to get the item. Did something bug out or is it part of the game. Also, it was not a seeded run. Thanks!
Best Answer
If what you're saying is that you received the achievement "The Mind", but the corresponding item didn't appear in the item chart or in game, that's how it's supposed to be.
Beating a boss only unlocks the item for the future, meaning that after beating the boss, you can find the item in subsequent runs.
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Can you unlock the lost with Azazel?
Die to the 2nd stage of the Satan boss fight as Azazel. This is the final step in unlocking The Lost, which means you cannot use a seed. Luckily Azazel is considered by many the easiest character.What do you do after you beat Mega Satan?
Killing him with The Lost, you need to do that for unlocking Godhead. no you just have to beat the chest or dark room. platinum god is the next step, and most people will unlock that at the same time with real platinum god anyway so really that's... it.How do you unlock Mega Satan in binding of Isaac Rebirth?
UnlockHow do you unlock the lost Boi?
The Lost is unlocked by dying 4 times in a row, each time with a certain character dying in a certain circumstance....Seeds can be used on all but the final step.How to Unlock The Mind and Holy Card (The Binding of Isaac Repentance)
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