So I used to be able to steal from merchants.

I successfully grabbed a Large Shield +1 and then put off stealing for a while because my pickpocket skill (which I think is what determines success chance) was pretty low.

At one point I was at a merchant and I noticed that they didn't have the steal option at the bottom. I figured it was an oddity, maybe like the churches which you can't steal from for some reason. But now I've gone around to numerous merchants, some of which I'm quite confident I could steal from before, and the option is gone.

What could cause this?

You still have a thief in the party? What are the specific stores?

Wowww, I must have not been paying proper attention. I could have sworn I could steal from a bunch of the stores that I'd been to before... I went back to the only store I've stolen from before and... I can still steal from it! I guess I was just totally wrong and misremembered that I could steal from a bunch of stores that I actually couldn't.

False alarm, thanks for replying, guys.