Stealing - A question

[Sithiel]

I just started playing a rogue character and sometimes I get the message 'You can't pry it away' and sometimes 'You failed'. Is this just a stylistic difference or are 'You can't pry it away' items for exam flagged non-stealable?

[Valyn]

Items that need to remain in a shopkeeper's inventory (because they're permanently part of the shop) typically can't be stolen and create the "You can't pry it away." echo you mentioned