I've yet to find the exact one I've been thinking of, but I did find this:

A monk asked, "I am speaking about the time when we haven't met each other; is there any relationship or not?"
The master said, "As there is perception, there is relationship."
The monk said, "If no other [person] is perceived, what is related to?"
The master said, "If it is not the case [that there is perception], it is your own self."
The monk said, "Can you be perceived or not?"
The master said, "As people move closer, the Way moves farther away."
The monk said, "Why do you hide yourself?"
The master said, "Right now I am openly talking with you."
The monk said, "How can you say you are not moving away?"
The master said, "Because it is obviously so [that I'm moving away]."