JavaJudt: I reached out to the city parks and rec department. The Recreation Superintendent responded, and confirmed that the ball fields are actually leased by athletic associations. So that would be up to them, not the city, for geocache permission (even though it is still a city park). He confirmed that the department is completely on board with geocaching in non-leased city parks.
Since it was requested this cache be removed, I am archiving it, and will be retrieving the container next time I am in town (planning for 5/20). Apologies to land managers for any trouble this has caused.
Unfortunately, I never thought I would have to archive an unfound cache! Thanks to everyone who has looked for it! I truly didn't intend for this to be too difficult of a hide, at least for experienced cachers - must be my hider's bias. In case anyone wants to know how this was hidden, I will post a spoiler photo when I retrieve it!