You are looking for a uniquely shaped container hidden in Highland Cemetery ... one of Lawton's "cities of the dead."
Día de (los) Muertos is a holiday traditionally celebrated on November 1-2, though other days, such as October 31, may be included depending on the locality. The multi-day holiday involves family and friends gathering to pay respects and remember to loved ones and acquaintances who have died. It is widely observed in Mexico, where it largely developed, and is also observed in other places by people of Mexican heritage. The observance falls during the Christian period of "Allhallowtide," of which All Hallow's Eve -- known to us as Halloween -- is a part.
Traditions connected with the holiday include honoring the deceased using decorative skulls and flowers, building home altars and enjoying the favorite foods and beverages of the departed, and visiting graves with these items as gifts for the deceased.
The celebration is not solely focused on the dead, as it is also common to give gifts to friends such as candy sugar skulls, to share traditional "pan de muerto" -- "bread of the dead," a sweet bread -- with family and friends, and to write light-hearted and often irreverent verses in the form of mock epitaphs dedicated to living friends and acquaintances, a literary form known as "calveras literarias."
It's highly recommended that you go after this one during daytime hours. As always, respect the residents.