I just noticed you said that they don't appear in your inventory - that could actually be normal, as they become just a number in your Ilithid Powers screen when picked up if you have already consumed one. Fun fact - you can steal any of them without repercussions because they "vanish into thin air" as soon as you loot them
Could it be that you have picked them up already? Press B and see if you have more parasites than you did before.
