Three short lines, and almost everything in them is about time passing. "Love used to live" tells us right away that something has ended. The verb is past tense, and the phrase "used to" carries a quiet ache, the way people talk about a place they can't go back to. Love is even described as if it were a person who once had an address, living "in the presence of the river."
Then the poem ends on a single image: a red handprint. The title, "Rock art," suggests the kind of mark people have left on stone for thousands of years, so the handprint reads like a signature, proof that someone was here. It's all that remains.
The speaker never says "I miss it," but the feeling comes through in the gap between the lines. The mood is hushed, wistful, and a little ancient. The river keeps flowing, while love survives only as a trace on rock.