Your field spell card was destroyed, and it's not part of the card effect to destroy harpies hunting ground, it's a rule that says only one field spell can be active at a time, and one was. It also works with things like Twister and Dust Tornado
so the part where your field card would gain counters to prevent in from being destroyed OR the destroying of the other field spell when you activated yours would been activated after the chained card --- however that card just happened to destroy your card first
Field spell cards usually act as continuous spell cards. Continuous spell cards only work when they're on the field. Every field card has a built in 'destroy any other field spell on the field' effect, but that effect only activated when it was already in the graveyard, and since field spells act as continuous spells, it didn't resolve.