Hmmm... Personally, I'm of the opinion that, in general, "I'm the guy you met...." is a bit weak, but the odd time it could still work, you never know.
This is where I like to use callback humour. When I meet a girl, ideally I'll try to make some kind of situational joke or maybe even give her some cocky/flirty nickname so that when I contact her next she automatically knows who it is without my having to look try-hard and emphasize my being a virtual stranger. Of course, these are things you have to have set up in that moment, and I'm going to assume since you didn't mention, that you didn't do that.
One girl I met backstage at a certain event she was modelling at, I didn't bother to text back for a week or two after I got her number (not a good idea by the way.) She gave me the dreaded "Who is this?" text. Instead of just giving a dry answer, which I felt put me in a weak position, I used some cocky banter, replying "Just how many ace [art] designers did you meet at [event]?!" Worked like a charm.
Of course, having left it for almost a year, she's not liable to remember anything at all, unless there was something extremely distinct about you or the situation or what you talked about. I can't really speak to this situation, other than to say that any attraction she may have had for you is probably gone so you're basically trying to go from zero.
"I'm the guy you met at the grocery store last year" type thing to me smells quite needy even if she does remember you, which she likely won't.
mmre's idea to add the "saw someone that looks exactly like you" is interesting.. that helps to lower the neediness element.
Or, maybe you could be more subtle and try something less definite, like "Why do you look really familiar.." (Disclaimer: I have never tried this!) To me, that carries much less risk of signalling to her that she is far more significant to you than you are to her. In fact, if she answers back with where/how you met, then you're in a really good position... but don't count on that happening.
Let us know back what happens.
And, just ignore this completely if I'm wrong, but reading between the lines, it seems you may not have much of an abundance mentality yet if you're worrying about some girl you met a year back and didn't talk to since, enough to join a forum to ask. You need to be approaching lots of girls. It's super-important. If you are, then great, carry on!
Cheers!
I recently saw someone that looks exactly like you and thought I'd drop a message^^ How are you doing?""
