Wild coins were available until the 2nd of December, 2012. Nowadays there are some known places where wild coins are, such as rare owned by value (/tele rare) where there is 3 wild coins.          

known coins by person    

Value 3 coins

pooa123 1 coin

Meep 1 coin

Grim 10 coins

Sage 3 coins

Hermit 1 coin

Xerp 2 coins

Coins can be picked up with (Q)Pickup tool. It was unfortunately tested by Montemayor on 1/24/15 after he found one behind his wall.             

          Ingame sprite of a wild coin.  -->