From wikipedia: "As of 2025, three interstellar objects have been discovered traveling through the Solar System: 1I/ʻOumuamua in 2017, 2I/Borisov in 2019, and 3I/ATLAS in 2025"

I would guess that observation improves over time. The wikipedia article is fascinating, estimating 10,000 such objects passing within Neptune's orbit in our solar system each day. I think that includes dust and sand sized objects.