I chose the skill extra pockets on my character which had on the thieves guild armour. when I receive the nightengale armour the extra pockets skill disappeared and I lost the extra 100 to my carring weight. Anyone else experience this and know why?

Do you get the Perk back if you change into other armor?

i found there are hidden ability in armor the thieves guild armor is useful if your spelunking the Nightengale armor suits me as an assassin like the dark brotherhood armor

so it might just be an armor specific perk

The perk disappeared? What platform are you on?

I can see you losing 50 points of carry weight, since you switched from TG armor, but I'm unsure where the other 50 went.

Did you also happen to switch standing stones? (i.e. Stead ---> something else)

I had on the first set of thieves guild armour. Chose the skill extra pockets. My carring weight went from 400 to 500. When I put on the Nightengale armour it went from 500 to 400. I am on the PC plateform. I haven't tried to take off the nightengale armour and put the thieves guild armour again. I can try that tonight. It svcks because I am carring to much weight without it. If it is armour specific they should say that because that would make it a unuseful skill. Chances are you are going to change armour after taking the skill.

It's not intended to be an armor specific perk, and I doubt that is what directly caused it. TG armor does have carry enchantments, so there's that to consider, but that doesn't add up either. Is it possible that you died and forgot to unlock the perk over again?