Did the latest patch or hotfix change how lockpicks work?
I know that trap disarming kits get used up every time you disarm, but lockpicks always remained as long as you were successful. I went to pick a lock last night and got the message that I had no lockpick kits left. That's impossible as I rarely fail those and had quite a bit of them.
But did you actually check your inventory? Maybe they were on a character that you weren't actively using in your party. Also, I'm not sure that disarm traps are used up every time you use one. I would've run out a long time ago on my current playthrough. I think the difference with lockpicking is that with lockpicking you can just try again without interruption but when you fail to disarm a trap, the kit is ruined and you set off the trap.