Are these only awarded via card play?
And when you use the effect from the token, do you discard the token?
That is correct. The only two ways for a Trader token(s) to come into play is from the Merchant character start game bonus or the Crooked Merchants action card.
The tokens section on page 15 should list the Trader token as another type of limited token. This means that players have to abide by token limitations when obtaining Trader tokens. This also means that once the token is used it is returned to the Bank.
This is another clarification that will be placed into the revised rule book. I am currently working on a FAQ/Errata document.