Tips for my lost my keys :'(?

About a month ago I lost my house keys at my ranch. I remember walking and them falling but I spent an hour with my cousin looking for them. They fell in the grass and we left without finding them. Now I was forced to tell my parents the story and they say that I must find them straight tomorrow morning. Due to people working at our ranch my dads afraid someone will find them and break in our house. ANY TIPS ARE APPRECIATED such as metal detector. I'm just looking for any helpful ways I can find . Thank you