I processed approximately 200 sims cards a while back. The sims I had were mostly from T-mobile and AT&T (these brands accounted for probably 2/3 of the sims I was working with) with a few other brands mixed in. I thought the same as you and put them in AP to soak. After all the foils were recovered, washed, dried and weighed they didn't even tip the scale. However, I did learn that I could use AP on Sims cards and there was gold to recover. In hindsight, I wish I had dissolved them separately from my other foils so I could have tested them with stannous to make absolutely sure there was gold content from the Sims but I had ***-u-me-d that the foils recovered were gold and I put them in the pot o' foils for future refining. If I ever come across them again I'm going to put them in with fingers if I don't have at least 1,000 or so to work with.
