Is your front door key on the same ring as your car key, and did you see it to enter your house?
reminds me of the number of times I found my Mum's keys in the back door when I was a teenager!!!
I did once loose my car keys when I first had my own house - all 3 sets of them!!!
eventually found them when I saw the dog with something on the front lawn when I was desperately looking through the car - which was fortunately unlocked
she was dropping something shiny - which turned out to be a set of car keys
found the other 2 sets in the grass on the back lawn - at a time of year that only the dog went out there mostly - certainly not me with car keys!!!
I kept then on special hook after that!!!