It would help people here to help you if you could tell us more about what has happened.
I think you're saying that you only viewed an item, but it was recorded as a sale. But you say that you did still want the item, but it was switched to something else. This doesn't sound like a rip-off by the seller - sellers can't mark items as bought when they were not, or change the item a buyer has bought to something else.
We can't see the listing involved, but It's more likely that there has been a mistake or misunderstanding. It's frustrating that the seller hasn't replied. How did you contact them? Have you sent them a formal cancellation request through eBay? Whatever the problem, the obvious solution wold be for the seller to cancel the sale, and then clarify exactly what you wish to buy from them.
If they don't reply to agree a cancellation all you can do is wait until they open an unaid item case against you. This will involve eBay, and be your opportunity to explain any confusion or wrong doing that you may feel was responsible.