The Ghost
You will know them by the silence after you hit send.
They were keen. Really keen. They wanted it done yesterday, loved your work, asked a dozen good questions. Then you sent the quote and they vanished into thin air. No yes, no no, no read receipt. Weeks later you still catch yourself wondering if you priced it wrong, or if they simply walked into the sea. You did nothing wrong. Ghosts ghost. It is who they are.
Stop chasing into the void. Send one warm follow-up at three days, one at ten, then close the file. Put an expiry on every quote ("valid 14 days") so the silence becomes their problem, not yours. And log where they came from, because a Ghost who found you through a bargain site is a different beast to one a good client referred.