In a case like this,there's not even the need for small claims - if you just contacted the better business bureau, you'd have gotten reimbursed the shipping and then something reasonable on top as 'an apology for the misunderstanding.'
Next time you have a straightforward 'they're wrong' issue with a company where you're getting outsourced flowcharts for support, try out the bbb. They're great.
Small claims would obviously also work, but that's a major investment in time/bureaucrazy, while a bbb complaint can be completed online in 10 minutes with maybe one or two brief follow-ups, but usually all it is, is them getting in contact with a human who can do things - and for cases like this, they obviously try to make it right.
I think you don't need even an oral agreement for a contract to be valid. Conclusive action is enough. Take a newspaper, but 2 USD on the table, leave. No words exchanged but valid sales contract established.