About once a month I cant find my phone when I know its at my house, just don't know where I last left it. After about 30 seconds of searching the house I just google "Find my Phone" and make it play a sound (I have an android) and find it immediately.
Side Note: Around 5 years ago I woke up with a raging hangover after sipping some barley pops with the bros and couldnt find my phone. I used this trick and could hear a faint ringing sound for a bit, flipped up all the couch cushions etc but never could actually find my phone and eventually it would not ring anymore. I figured I must still be intoxicate and that I was just hearing things, really messed me up.
I started retracing my night and eventually that evening got ahold of the UBER driver that drove me home. My phone fell out of my pocket in the backseat and he noticed it later in the night and dropped it back off in my mailbox....So I was not actually going crazy, my phone was just outside of my house in my mailbox and the battery died after a couple of rings.