You shouldn't have said it was your mum's garden and roll with it! You could have invented a story, about how you inherited this garden from a stranger, that died right in front of your porch, handling you a shovel and with his dying breath he said: "You gotta dig now".
He was talking about his potatoes, but you took it literally and dug a grave for him instead.
The End
Hahaha, I'm way too honest. Wouldn't even cross my mind to make up something 🙂
That's what the best liars say 😂😎😉