Angela,
You can set up "other" as a payment option in your shop. This is done for several reasons. One of them being trades.
The reason I say it could have been intentional is, when I was a buyer (not a seller), I almost completed a transaction as "other". I was more or less curious how far the sale would go without putting in any payment. I thought, Wow I can buy this and not pay. How strange! When I actually did it as part of a trade, I was surprised ow quick the transaction was done and no verification of anything was needed.
I also think, if you're sending a convo, buyers don't get on Etsy like we do. They rarely check their convos. Also, life happens. Unlike us, the last thing a buyer is thinking about is their Etsy account.