I'm not sure if it matters which game you are playing but I believe if you're lock pick is not high enough, you get a message that you failed and it won't work until you invest more in points.

oh my goodness duh! my bad im on divine divinity if its any different from other games.

I won't be of much help due to how long it's been but I believe in DD, lock picks can be broke because I remember a set of magic ones that you can give to someone to complete a side quest or keep because they don't break. I still think that the pick simply will not work (and you lose a pick) if your level isn't high enough but it sounds like that didn't happen for you. I'll ask about it on the Larian site - not much activity for DD but I might get lucky.