Thinking About Thinking About You

I want to start this poem saying
The last time I saw you
But I've already started a poem that way
But those words stick in my brain
Like a song that won't go away
If only I knew who you are or were
Who is the you in you?
And when was the last time I saw you?
It would certainly be good to know
Provide context
Instead, my mind latches on to the last time I saw you
And so it goes
Thinking about you
Thinking about thinking about you
Someone I may or not know
But somewhere, I do
Somewhere, I'm thinking about the last time I saw you
It's memorable
Over and over
Obsessed by it
Or so I'm told