Brief summary of Breakthrough Starshot: This is an idea to send hundreds of gram-scale craft with meter-scale light sails propelled to the Alpha Centauri star system at 15-20% light speed using a phased laser array.

I don't think we'd be able to see probes this small moving this fast with the LSST. But should we be able to see them hit the Moon or explode in our atmosphere?

If we assume the same rough parameters, would the probes be moving too fast for us to be able to determine if they were interstellar in origin or not? Could we figure it out if we happened to see one impact the Moon without being able to record the precise inbound course? Are there any other ways we might be able to spot probes like this?