No you're fine in that situation. That communication is automatically privileged, even if the attorney doesn't take your case, because it was part of a communication soliciting legal advice.

It’s not clear cut if you haven’t discussed terms, representation, etc. the attorney might say, “I’m booked” before asking additional information.

That's irrelevant from the point of view of the privilege applying. What matters is that the communication was for the purposes of soliciting legal advice from an attorney, otherwise the DA could just subpoena an attorney that the defendant talked to but was unable to afford or who was too busy to handle the particulars of the defendant's case.

That's not how I read it:

"The establishment of the attorney-client relationship involves two elements: a person seeks advice or assistance from an attorney; and the attorney appears to give, agrees to give or gives the advice or assistance[1]"

and

"That “special relationship” between an attorney and his/her client is generally established by mutual assent/consent. This is most often confirmed by a written “retainer”[2]"

Other states have similar determinants.

[1]https://www.lsba.org/PracticeAidGuide/PAG1.aspx

[2]https://attorneys.uslegal.com/malpractice/establishing-the-a...