Ask Why do some clients disappear after you send a proposal they personally asked you to write?

[Brendan]

I have noticed that some clients reach out, ask you to write a full proposal with details and pricing, and then go completely silent once you send it. No reply, no explanation, nothing. It feels strange because they were the ones who started the conversation. Some people think the client was never serious, while others believe they just used the proposal to understand the market rate. Has this ever happened to you, and what do you think is really going on?