I just purchased the 21 in. 56-Volt Lith-ion Electric Cordless Poly Deck Dual-Port Self Propelled Walk Behind Mower 2X 5.0Ah Batteries ( peak performance). While I was unboxing the mower a small oval/circular plastic piece remained in the box. The lawnmower works fine. I'm concerned this small piece belongs somewhere. All the packaging is cardboard. Did anyone find this piece while unboxing? I'm tempted to return it to Home Depot and get a fresh one just in case.