From what I've read (and observed on numerous occasions) Silver is a low rate spawn in the location of a Tin vein and Gold is the same way for an Iron vein. This means that if you camp out by a Tin vein and wait for it to respawn, once in a while it will spawn as Silver. I haven't seen anything written about it but I think the same thing happens with Truesilver in Mithril veins.
To answer your question, follow your Tin maps and you should occasinally find Silver. I haven't used the database so I can't input anything on that.