I used to work for Wetherspoons, although I quit a couple of years ago, before work trials had really come in. Knowing the company though the habitually pay-docking little pieces of excrement they probably brought work trials in because they wanted free, willing labour for an afternoon. However, all they really want in an employee is someone who is willing, compliant and tries their best; I saw some absolute idiots be taken on.
It sounds like you were pipped to the post this time because someone else had experience. If there are other Wetherspoons in your town, then try applying to them. There's no communication between different pubs, and so you can start afresh with them, knowing what you know from your previous work trial (just don't mention that you have previously had a work trial!)
Finally - try hospitality agencies. They only want bodies with a pulse, and often don't care if you don't have any experience - but working for an agency gives you a vast array of experience that you could never get in a "steady" job - I've more than lost track of all the venues I've worked at through agencies.