This resonates with me because i have been in a similar situation. In my own case, i was eager to get them onboard (they agreed to my fee and the money was good). After 3 hours of answering their questions and giving a step by step description on what i would write, they ended up ghosting me. I am pretty sure they used my idea though, although they refused to share their website name (that should have been the first red flag, lol), so i have no way of knowing. The questions were too specific for it not to be used.
I have learned and moved on. Other buyers have tried similar tactics with me, including returning buyers. I give vague replies and tell them to tell me what they want. Most of them don't come back.