You can actually accomplish this pretty easily with off the shelf components! You can just say, "Hey, I think we've met before but I can't remember exactly where?"
It also works really well as a conversation starter for me. I forget people’s names and the context all the time, but the faces stay familiar, and of course you can tell from their facial expression that we’ve met.
Showoff. I can't remember names or recognise faces. I've settled on a strategy of simply greeting everyone as though I've met them before, which feels a lot more empathic than sending everyone I meet's details to a mass surveillance company.
I sometimes have trouble recognizing faces and sometimes it’s quite embarrassing (like when it’s one of your in laws or running into an important customer at a conference.