I really don’t see a ball being dropped, so I guess we’ll have to agree to disagree there.
We don’t have DA’s in Iowa, we have county attorneys. You should probably not take everything you see on TV and apply it to real life. But anyway.
Something like your situation, the roommate either ratted you out on the paraphernalia or it was found in your bedroom, bag, etc. The officer must of had some probable cause linking it to you in order to submit a warrant request to judge that was subsequently ordered.
On a warrant for possession of drug paraphernalia, they’re going to issue it and enter it into NCIC. (Someone running your name in Wisconsin or Minnesota wouldn’t even see it if it were just for Johnson Co, bordering counties, 100 miles. It would be Iowa only basically that would see it). They won’t contact you, likely not go looking for you in most cities, nor would they contact the state marshal (DCI?). They will just wait for your next interaction with law enforcement and handle it then.
Even more, by the sounds of it, you interacted with law enforcement outside the limits of extradition. He was not obligated to inform you about your warrant in Johnson Co. Many times they won’t.