B737-800 Captain reported communications problems with Maintenance concerning correct documentation for Company Material loaded on the aircraft that was HAZMAT.

Narrative

Landed a little over 30 minutes late in ZZZ. Following deplaning; the Ops Agent asked us what kind of mechanical problem we had. I told him that we had an MEL for a Wingtip Position light; but otherwise had no issues. He said local Ops told him that Maintenance was on the way to 'work on the aircraft.' We again told him we didn't call anything in and were not aware of any issues. He then sat in the aisle chair in the jet way and was not going to board until Maintenance showed up or Ops contacted him. At that point; I called Dispatch and asked if there was a lock on the flight or if he was aware of any Maintenance that was required to be done on the aircraft. He said he showed no lock and was not aware of anything either. I shared that information with the Ops agent and he readily agreed to board the aircraft. There was definitely some communication issues and my FO and I thought maybe they had notified the wrong gate; etc. Following boarding; and just prior to push; a ops rep showed up on the flight deck with NOTAC paperwork and said we had a battery on board. I signed the paperwork; gave him a copy and proceeded with the Before Push Checklist; as we were ready to go at that point.