What is it that I have been passing?

I just finished with my second flush yesterday. My husband who is away right now begged me to save a few of the stones for him to see so I fished out a few and put them in a jar with vinegar. This morning when I woke up I noticed that the stones had literally dissolved and there was just a few floating particals in the jar. I thought I read that vinegar works to keep them. Am I wrong?
The two stones I chose where just like the rest. (I passed about 80-100 on both flushes).
So now I feel sad. Am I really not passing stones?
Any expereince with this?