Who said anything about a study? No study is needed to see that you obviously don’t understand what revealed preference means, you are contradicting the definition of the economic term.

Take your question. The reason someone might do something different from what they said could be due to anything, such as constraints like cost, time, or availability. It could be due to changing circumstances, or someone else’s preferences. Any given answer to your question cannot be used to infer anything about preference, and assuming it does means you’re not thinking scientifically.

Revealed preference theory is trying to demonstrate what can be proven about preference, which is why it requires a situation where someone spends money on a mutually exclusive choice between two things that are close enough to be an apples to apples comparison. If you don’t do that, then you’re fooling yourself about what the data means.